Class | Sequel::Dataset

In:

lib/sequel/adapters/do.rb
lib/sequel/adapters/jdbc.rb
lib/sequel/adapters/mysql.rb
lib/sequel/adapters/postgres.rb
lib/sequel/adapters/sqlite.rb
lib/sequel/adapters/utils/stored_procedures.rb
lib/sequel/adapters/swift.rb
lib/sequel/dataset.rb
lib/sequel/dataset/actions.rb
lib/sequel/dataset/features.rb
lib/sequel/dataset/graph.rb
lib/sequel/dataset/misc.rb
lib/sequel/dataset/prepared_statements.rb
lib/sequel/dataset/query.rb
lib/sequel/dataset/sql.rb
lib/sequel/dataset/mutation.rb
lib/sequel/extensions/pagination.rb
lib/sequel/extensions/pretty_table.rb
lib/sequel/extensions/query.rb
lib/sequel/extensions/to_dot.rb
lib/sequel/extensions/columns_introspection.rb

Parent: | Sequel::Dataset

A dataset represents an SQL query, or more generally, an abstract set of rows in the database. Datasets can be used to create, retrieve, update and delete records.

Query results are always retrieved on demand, so a dataset can be kept around and reused indefinitely (datasets never cache results):

      my_posts = DB[:posts].filter(:author => 'david') # no records are retrieved
      my_posts.all # records are retrieved
      my_posts.all # records are retrieved again

Most dataset methods return modified copies of the dataset (functional style), so you can reuse different datasets to access data:

      posts = DB[:posts]
      davids_posts = posts.filter(:author => 'david')
      old_posts = posts.filter('stamp < ?', Date.today - 7)
      davids_old_posts = davids_posts.filter('stamp < ?', Date.today - 7)

Datasets are Enumerable objects, so they can be manipulated using any of the Enumerable methods, such as map, inject, etc.

For more information, see the "Dataset Basics" guide.

### Contents

- 2 - Methods that execute code on the database
- 4 - Methods that describe what the dataset supports
- 5 - Methods related to dataset graphing
- 6 - Miscellaneous methods
- 8 - Methods related to prepared statements or bound variables
- 1 - Methods that return modified datasets
- 3 - User Methods relating to SQL Creation
- 9 - Internal Methods relating to SQL Creation
- 7 - Mutation methods

### Methods

<< == [] []= _import _insert_sql _select_map_multiple _select_map_single _update_sql add_graph_aliases aliased_expression_sql_append all and array_sql_append avg bind boolean_constant_sql_append call call call case_expression_sql_append cast_sql_append clause_methods clone column_all_sql_append columns columns! columns_without_introspection complex_expression_sql_append compound_clone compound_from_self constant_sql_append count def_append_methods def_mutation_method def_mutation_method delete delete delete_sql distinct each each_page each_server empty? eql? except exclude exclude_having exclude_where exists fetch_rows fetch_rows fetch_rows fetch_rows fetch_rows fetch_rows fetch_rows filter first first_source first_source_alias first_source_table for_update from from_self function_sql_append get graph graph grep group group_and_count group_by group_cube group_rollup hash having identifier_input_method identifier_output_method import insert insert insert_multiple insert_sql inspect intersect interval introspect_all_columns invert join join_clause_sql_append join_on_clause_sql_append join_table join_using_clause_sql_append last limit literal_append lock_style map max min multi_insert multi_insert_sql naked naked! negative_boolean_constant_sql_append new options_overlap or order order_append order_by order_more order_prepend ordered_expression_sql_append paginate placeholder_literal_string_sql_append prepare prepare prepare prepare prepared_arg_placeholder print provides_accurate_rows_matched? qualified_identifier_sql_append qualify qualify_to qualify_to_first_source query quote_identifier_append quote_identifiers? quote_schema_table_append quoted_identifier_append range recursive_cte_requires_column_aliases? replace requires_placeholder_type_specifiers? requires_sql_standard_datetimes? returning reverse reverse_order row_number_column schema_and_table select select_all select_append select_group select_hash select_map select_more select_order_map select_sql server set set_defaults set_graph_aliases set_overrides simple_select_all? single_record single_value split_alias split_multiple_result_sets sql subscript_sql_append sum supports_cte? supports_cte_in_subqueries? supports_distinct_on? supports_group_cube? supports_group_rollup? supports_insert_select? supports_intersect_except? supports_intersect_except_all? supports_is_true? supports_join_using? supports_modifying_joins? supports_multiple_column_in? supports_ordered_distinct_on? supports_returning? supports_select_all_and_column? supports_timestamp_timezones? supports_timestamp_usecs? supports_where_true? supports_window_functions? to_csv to_dot to_hash to_prepared_statement truncate truncate_sql unbind unfiltered ungraphed ungrouped union unlimited unordered unused_table_alias update update update_sql use_cursor where window_function_sql_append window_sql_append with with_recursive with_sql

### Included Modules

StoredProcedures Sequel::MySQL::DatasetMethods Sequel::MySQL::PreparedStatements::DatasetMethods Sequel::Postgres::DatasetMethods ::Sequel::SQLite::DatasetMethods Metaprogramming Enumerable SQL::AliasMethods SQL::BooleanMethods SQL::CastMethods SQL::ComplexExpressionMethods SQL::InequalityMethods SQL::NumericMethods SQL::OrderMethods SQL::StringMethods ColumnsIntrospection

### Classes and Modules

Module Sequel::Dataset::ArgumentMapper
Module Sequel::Dataset::BindArgumentMethods
Module Sequel::Dataset::PreparedStatementMethods
Module Sequel::Dataset::StoredProcedureMethods
Module Sequel::Dataset::StoredProcedures
Class Sequel::Dataset::TYPE_TRANSLATOR

### Constants

DatasetClass | = | self
DatasetClass | = | self
JAVA_SQL_TIMESTAMP | = | Java::JavaSQL::Timestamp |  | Cache Java class constants to speed up lookups
JAVA_SQL_TIME | = | Java::JavaSQL::Time
JAVA_SQL_DATE | = | Java::JavaSQL::Date
JAVA_SQL_BLOB | = | Java::JavaSQL::Blob
JAVA_SQL_CLOB | = | Java::JavaSQL::Clob
JAVA_BUFFERED_READER | = | Java::JavaIo::BufferedReader
JAVA_BIG_DECIMAL | = | Java::JavaMath::BigDecimal
JAVA_BYTE_ARRAY | = | Java::byte[]
TYPE_TRANSLATOR_INSTANCE | = | tt = TYPE_TRANSLATOR.new
DECIMAL_METHOD | = | tt.method(:decimal) |  | Cache type translator methods so that duplicate Method objects are not created.
TIME_METHOD | = | tt.method(:time)
DATE_METHOD | = | tt.method(:date)
BUFFERED_READER_METHOD | = | tt.method(:buffered_reader)
BYTE_ARRAY_METHOD | = | tt.method(:byte_array)
BLOB_METHOD | = | tt.method(:blob)
CLOB_METHOD | = | tt.method(:clob)
DatasetClass | = | self
DatasetClass | = | self
PREPARED_ARG_PLACEHOLDER | = | LiteralString.new('$').freeze
DatasetClass | = | self
PREPARED_ARG_PLACEHOLDER | = | ':'.freeze
DatasetClass | = | self

### Attributes

convert_types | [RW] | Whether to convert some Java types to ruby types when retrieving rows. Uses the database‘s setting by default, can be set to false to roughly double performance when fetching rows.

### Public Instance methods

call(type, bind_vars={}, *values, &block)

Execute the given type of statement with the hash of values.

[Source]

         # File lib/sequel/adapters/sqlite.rb, line 288
    288:       def call(type, bind_vars={}, *values, &block)
    289:         ps = to_prepared_statement(type, values)
    290:         ps.extend(BindArgumentMethods)
    291:         ps.call(bind_vars, &block)
    292:       end

call(type, bind_vars={}, *values, &block)

Execute the given type of statement with the hash of values.

[Source]

         # File lib/sequel/adapters/postgres.rb, line 585
    585:         def call(type, bind_vars={}, *values, &block)
    586:           ps = to_prepared_statement(type, values)
    587:           ps.extend(BindArgumentMethods)
    588:           ps.call(bind_vars, &block)
    589:         end

delete()

Delete rows matching this dataset

[Source]

         # File lib/sequel/adapters/mysql.rb, line 273
    273:       def delete
    274:         execute_dui(delete_sql){|c| return c.affected_rows}
    275:       end

fetch_rows(sql) {|h| ...}

Execute the SQL on the database and yield the rows as hashes with symbol keys.

[Source]

         # File lib/sequel/adapters/do.rb, line 156
    156:       def fetch_rows(sql)
    157:         execute(sql) do |reader|
    158:           cols = @columns = reader.fields.map{|f| output_identifier(f)}
    159:           while(reader.next!) do
    160:             h = {}
    161:             cols.zip(reader.values).each{|k, v| h[k] = v}
    162:             yield h
    163:           end
    164:         end
    165:         self
    166:       end

fetch_rows(sql) {|row| ...}

Yield a hash for each row in the dataset.

[Source]

         # File lib/sequel/adapters/sqlite.rb, line 295
    295:       def fetch_rows(sql)
    296:         execute(sql) do |result|
    297:           i = -1
    298:           cps = db.conversion_procs
    299:           type_procs = result.types.map{|t| cps[base_type_name(t)]}
    300:           cols = result.columns.map{|c| i+=1; [output_identifier(c), i, type_procs[i]]}
    301:           @columns = cols.map{|c| c.first}
    302:           result.each do |values|
    303:             row = {}
    304:             cols.each do |name,i,type_proc|
    305:               v = values[i]
    306:               if type_proc && v.is_a?(String)
    307:                 v = type_proc.call(v)
    308:               end
    309:               row[name] = v
    310:             end
    311:             yield row
    312:           end
    313:         end
    314:       end

fetch_rows(sql, &block)

Correctly return rows from the database and return them as hashes.

[Source]

         # File lib/sequel/adapters/jdbc.rb, line 593
    593:       def fetch_rows(sql, &block)
    594:         execute(sql){|result| process_result_set(result, &block)}
    595:         self
    596:       end

fetch_rows(sql, &block)

Set the columns and yield the hashes to the block.

[Source]

         # File lib/sequel/adapters/swift.rb, line 138
    138:       def fetch_rows(sql, &block)
    139:         execute(sql) do |res|
    140:           @columns = res.fields
    141:           res.each(&block)
    142:         end
    143:         self
    144:       end

fetch_rows(sql) {|s| ...}

Yield all rows matching this dataset. If the dataset is set to split multiple statements, yield arrays of hashes one per statement instead of yielding results for all statements as hashes.

[Source]

         # File lib/sequel/adapters/mysql.rb, line 280
    280:       def fetch_rows(sql, &block)
    281:         execute(sql) do |r|
    282:           i = -1
    283:           cps = db.conversion_procs
    284:           cols = r.fetch_fields.map do |f|
    285:             # Pretend tinyint is another integer type if its length is not 1, to
    286:             # avoid casting to boolean if Sequel::MySQL.convert_tinyint_to_bool
    287:             # is set.
    288:             type_proc = f.type == 1 && f.length != 1 ? cps[2] : cps[f.type]
    289:             [output_identifier(f.name), type_proc, i+=1]
    290:           end
    291:           @columns = cols.map{|c| c.first}
    292:           if opts[:split_multiple_result_sets]
    293:             s = []
    294:             yield_rows(r, cols){|h| s << h}
    295:             yield s
    296:           else
    297:             yield_rows(r, cols, &block)
    298:           end
    299:         end
    300:         self
    301:       end

fetch_rows(sql, &block)

Yield all rows returned by executing the given SQL and converting the types.

[Source]

         # File lib/sequel/adapters/postgres.rb, line 466
    466:       def fetch_rows(sql, &block)
    467:         return cursor_fetch_rows(sql, &block) if @opts[:cursor]
    468:         execute(sql){|res| yield_hash_rows(res, fetch_rows_set_cols(res), &block)}
    469:       end

graph(*)

Don‘t allow graphing a dataset that splits multiple statements

[Source]

         # File lib/sequel/adapters/mysql.rb, line 304
    304:       def graph(*)
    305:         raise(Error, "Can't graph a dataset that splits multiple result sets") if opts[:split_multiple_result_sets]
    306:         super
    307:       end

insert(*values)

Insert a new value into this dataset

[Source]

         # File lib/sequel/adapters/mysql.rb, line 310
    310:       def insert(*values)
    311:         execute_dui(insert_sql(*values)){|c| return c.insert_id}
    312:       end

prepare(type, name=nil, *values)

Create a named prepared statement that is stored in the database (and connection) for reuse.

[Source]

         # File lib/sequel/adapters/jdbc.rb, line 600
    600:       def prepare(type, name=nil, *values)
    601:         ps = to_prepared_statement(type, values)
    602:         ps.extend(PreparedStatementMethods)
    603:         if name
    604:           ps.prepared_statement_name = name
    605:           db.prepared_statements[name] = ps
    606:         end
    607:         ps
    608:       end

prepare(type, name=nil, *values)

Prepare the given type of statement with the given name, and store it in the database to be called later.

[Source]

         # File lib/sequel/adapters/postgres.rb, line 593
    593:         def prepare(type, name=nil, *values)
    594:           ps = to_prepared_statement(type, values)
    595:           ps.extend(PreparedStatementMethods)
    596:           if name
    597:             ps.prepared_statement_name = name
    598:             db.prepared_statements[name] = ps
    599:           end
    600:           ps
    601:         end

prepare(type, name=nil, *values)

Prepare the given type of query with the given name and store it in the database. Note that a new native prepared statement is created on each call to this prepared statement.

[Source]

         # File lib/sequel/adapters/sqlite.rb, line 319
    319:       def prepare(type, name=nil, *values)
    320:         ps = to_prepared_statement(type, values)
    321:         ps.extend(PreparedStatementMethods)
    322:         if name
    323:           ps.prepared_statement_name = name
    324:           db.prepared_statements[name] = ps
    325:         end
    326:         ps
    327:       end

prepared_arg_placeholder()

PostgreSQL uses $N for placeholders instead of ?, so use a $ as the placeholder.

[Source]

         # File lib/sequel/adapters/postgres.rb, line 607
    607:         def prepared_arg_placeholder
    608:           PREPARED_ARG_PLACEHOLDER
    609:         end

replace(*args)

Replace (update or insert) the matching row.

[Source]

         # File lib/sequel/adapters/mysql.rb, line 315
    315:       def replace(*args)
    316:         execute_dui(replace_sql(*args)){|c| return c.insert_id}
    317:       end

split_multiple_result_sets()

Makes each yield arrays of rows, with each array containing the rows for a given result set. Does not work with graphing. So you can submit SQL with multiple statements and easily determine which statement returned which results.

Modifies the row_proc of the returned dataset so that it still works as expected (running on the hashes instead of on the arrays of hashes). If you modify the row_proc afterward, note that it will receive an array of hashes instead of a hash.

[Source]

         # File lib/sequel/adapters/mysql.rb, line 328
    328:       def split_multiple_result_sets
    329:         raise(Error, "Can't split multiple statements on a graphed dataset") if opts[:graph]
    330:         ds = clone(:split_multiple_result_sets=>true)
    331:         ds.row_proc = proc{|x| x.map{|h| row_proc.call(h)}} if row_proc
    332:         ds
    333:       end

update(values={})

Update the matching rows.

[Source]

         # File lib/sequel/adapters/mysql.rb, line 336
    336:       def update(values={})
    337:         execute_dui(update_sql(values)){|c| return c.affected_rows}
    338:       end

use_cursor(opts={})

Uses a cursor for fetching records, instead of fetching the entire result set at once. Can be used to process large datasets without holding all rows in memory (which is what the underlying drivers do by default). Options:

- :rows_per_fetch - the number of rows per fetch (default 1000). Higher numbers result in fewer queries but greater memory use.

Usage:

      DB[:huge_table].use_cursor.each{|row| p row}
      DB[:huge_table].use_cursor(:rows_per_fetch=>10000).each{|row| p row}

This is untested with the prepared statement/bound variable support, and unlikely to work with either.

[Source]

         # File lib/sequel/adapters/postgres.rb, line 486
    486:       def use_cursor(opts={})
    487:         clone(:cursor=>{:rows_per_fetch=>1000}.merge(opts))
    488:       end

## 2 - Methods that execute code on the database

These methods all execute the dataset‘s SQL on the database. They don‘t return modified datasets, so if used in a method chain they should be the last method called.

### Constants

ACTION_METHODS

=

(<<-METHS).split.map{|x| x.to_sym} << [] []= all avg count columns columns! delete each empty? fetch_rows first get import insert insert_multiple interval last map max min multi_insert range select_hash select_map select_order_map set single_record single_value sum to_csv to_hash truncate update METHS ).split.map{|x| x.to_sym}

Action methods defined by Sequel that execute code on the database.

### Public Instance methods

<<(arg)

Inserts the given argument into the database. Returns self so it can be used safely when chaining:

      DB[:items] << {:id=>0, :name=>'Zero'} << DB[:old_items].select(:id, name)

[Source]

        # File lib/sequel/dataset/actions.rb, line 23
    23:     def <<(arg)
    24:       insert(arg)
    25:       self
    26:     end

[](*conditions)

Returns the first record matching the conditions. Examples:

      DB[:table][:id=>1] # SELECT * FROM table WHERE (id = 1) LIMIT 1
      # => {:id=1}

[Source]

        # File lib/sequel/dataset/actions.rb, line 32
    32:     def [](*conditions)
    33:       raise(Error, ARRAY_ACCESS_ERROR_MSG) if (conditions.length == 1 and conditions.first.is_a?(Integer)) or conditions.length == 0
    34:       first(*conditions)
    35:     end

[]=(conditions, values)

Update all records matching the conditions with the values specified. Returns the number of rows affected.

      DB[:table][:id=>1] = {:id=>2} # UPDATE table SET id = 2 WHERE id = 1
      # => 1 # number of rows affected

[Source]

        # File lib/sequel/dataset/actions.rb, line 42
    42:     def []=(conditions, values)
    43:       filter(conditions).update(values)
    44:     end

all(&block)

Returns an array with all records in the dataset. If a block is given, the array is iterated over after all items have been loaded.

      DB[:table].all # SELECT * FROM table
      # => [{:id=>1, ...}, {:id=>2, ...}, ...]

      # Iterate over all rows in the table
      DB[:table].all{|row| p row}

[Source]

        # File lib/sequel/dataset/actions.rb, line 54
    54:     def all(&block)
    55:       a = []
    56:       each{|r| a << r}
    57:       post_load(a)
    58:       a.each(&block) if block
    59:       a
    60:     end

avg(column)

Returns the average value for the given column.

      DB[:table].avg(:number) # SELECT avg(number) FROM table LIMIT 1
      # => 3

[Source]

        # File lib/sequel/dataset/actions.rb, line 66
    66:     def avg(column)
    67:       aggregate_dataset.get{avg(column)}
    68:     end

columns()

Returns the columns in the result set in order as an array of symbols. If the columns are currently cached, returns the cached value. Otherwise, a SELECT query is performed to retrieve a single row in order to get the columns.

If you are looking for all columns for a single table and maybe some information about each column (e.g. database type), see `Database#schema`.

      DB[:table].columns
      # => [:id, :name]

[Source]

        # File lib/sequel/dataset/actions.rb, line 79
    79:     def columns
    80:       return @columns if @columns
    81:       ds = unfiltered.unordered.clone(:distinct => nil, :limit => 1, :offset=>nil)
    82:       ds.each{break}
    83:       @columns = ds.instance_variable_get(:@columns)
    84:       @columns || []
    85:     end

columns!()

Ignore any cached column information and perform a query to retrieve a row in order to get the columns.

      DB[:table].columns!
      # => [:id, :name]

[Source]

        # File lib/sequel/dataset/actions.rb, line 92
    92:     def columns!
    93:       @columns = nil
    94:       columns
    95:     end

count()

Returns the number of records in the dataset.

      DB[:table].count # SELECT COUNT(*) AS count FROM table LIMIT 1
      # => 3

[Source]

         # File lib/sequel/dataset/actions.rb, line 101
    101:     def count
    102:       aggregate_dataset.get{COUNT(:*){}.as(count)}.to_i
    103:     end

delete(&block)

Deletes the records in the dataset. The returned value should be number of records deleted, but that is adapter dependent.

      DB[:table].delete # DELETE * FROM table
      # => 3

[Source]

         # File lib/sequel/dataset/actions.rb, line 110
    110:     def delete(&block)
    111:       sql = delete_sql
    112:       if uses_returning?(:delete)
    113:         returning_fetch_rows(sql, &block)
    114:       else
    115:         execute_dui(sql)
    116:       end
    117:     end

each() {|row_proc.call(r)}| ...}

Iterates over the records in the dataset as they are yielded from the database adapter, and returns self.

      DB[:table].each{|row| p row} # SELECT * FROM table

Note that this method is not safe to use on many adapters if you are running additional queries inside the provided block. If you are running queries inside the block, you should use `all` instead of `each` for the outer queries, or use a separate thread or shard inside `each`:

[Source]

         # File lib/sequel/dataset/actions.rb, line 128
    128:     def each(&block)
    129:       if @opts[:graph]
    130:         graph_each(&block)
    131:       elsif row_proc = @row_proc
    132:         fetch_rows(select_sql){|r| yield row_proc.call(r)}
    133:       else
    134:         fetch_rows(select_sql, &block)
    135:       end
    136:       self
    137:     end

empty?()

Returns true if no records exist in the dataset, false otherwise

      DB[:table].empty? # SELECT 1 AS one FROM table LIMIT 1
      # => false

[Source]

         # File lib/sequel/dataset/actions.rb, line 143
    143:     def empty?
    144:       get(Sequel::SQL::AliasedExpression.new(1, :one)).nil?
    145:     end

fetch_rows(sql)

Executes a select query and fetches records, yielding each record to the supplied block. The yielded records should be hashes with symbol keys. This method should probably should not be called by user code, use `each` instead.

[Source]

         # File lib/sequel/dataset/actions.rb, line 151
    151:     def fetch_rows(sql)
    152:       raise NotImplemented, NOTIMPL_MSG
    153:     end

first(*args, &block)

If a integer argument is given, it is interpreted as a limit, and then returns all matching records up to that limit. If no argument is passed, it returns the first matching record. If any other type of argument(s) is passed, it is given to filter and the first matching record is returned. If a block is given, it is used to filter the dataset before returning anything. Examples:

      DB[:table].first # SELECT * FROM table LIMIT 1
      # => {:id=>7}

      DB[:table].first(2) # SELECT * FROM table LIMIT 2
      # => [{:id=>6}, {:id=>4}]

      DB[:table].first(:id=>2) # SELECT * FROM table WHERE (id = 2) LIMIT 1
      # => {:id=>2}

      DB[:table].first("id = 3") # SELECT * FROM table WHERE (id = 3) LIMIT 1
      # => {:id=>3}

      DB[:table].first("id = ?", 4) # SELECT * FROM table WHERE (id = 4) LIMIT 1
      # => {:id=>4}

      DB[:table].first{id > 2} # SELECT * FROM table WHERE (id > 2) LIMIT 1
      # => {:id=>5}

      DB[:table].first("id > ?", 4){id < 6} # SELECT * FROM table WHERE ((id > 4) AND (id < 6)) LIMIT 1
      # => {:id=>5}

      DB[:table].first(2){id < 2} # SELECT * FROM table WHERE (id < 2) LIMIT 2
      # => [{:id=>1}]

[Source]

         # File lib/sequel/dataset/actions.rb, line 185
    185:     def first(*args, &block)
    186:       ds = block ? filter(&block) : self
    187:
    188:       if args.empty?
    189:         ds.single_record
    190:       else
    191:         args = (args.size == 1) ? args.first : args
    192:         if Integer === args
    193:           ds.limit(args).all
    194:         else
    195:           ds.filter(args).single_record
    196:         end
    197:       end
    198:     end

get(column=nil, &block)

Return the column value for the first matching record in the dataset. Raises an error if both an argument and block is given.

      DB[:table].get(:id) # SELECT id FROM table LIMIT 1
      # => 3

      ds.get{sum(id)} # SELECT sum(id) FROM table LIMIT 1
      # => 6

[Source]

         # File lib/sequel/dataset/actions.rb, line 208
    208:     def get(column=nil, &block)
    209:       if column
    210:         raise(Error, ARG_BLOCK_ERROR_MSG) if block
    211:         select(column).single_value
    212:       else
    213:         select(&block).single_value
    214:       end
    215:     end

import(columns, values, opts={})

Inserts multiple records into the associated table. This method can be used to efficiently insert a large number of records into a table in a single query if the database supports it. Inserts are automatically wrapped in a transaction.

This method is called with a columns array and an array of value arrays:

      DB[:table].import([:x, :y], [[1, 2], [3, 4]])
      # INSERT INTO table (x, y) VALUES (1, 2)
      # INSERT INTO table (x, y) VALUES (3, 4)

This method also accepts a dataset instead of an array of value arrays:

      DB[:table].import([:x, :y], DB[:table2].select(:a, :b))
      # INSERT INTO table (x, y) SELECT a, b FROM table2

Options:

:commit_every : | Open a new transaction for every given number of records. For example, if you provide a value of 50, will commit after every 50 records.
:server : | Set the server/shard to use for the transaction and insert queries.
:slice : | Same as :commit_every, :commit_every takes precedence.

[Source]

         # File lib/sequel/dataset/actions.rb, line 240
    240:     def import(columns, values, opts={})
    241:       return @db.transaction{insert(columns, values)} if values.is_a?(Dataset)
    242:
    243:       return if values.empty?
    244:       raise(Error, IMPORT_ERROR_MSG) if columns.empty?
    245:       ds = opts[:server] ? server(opts[:server]) : self
    246:
    247:       if slice_size = opts[:commit_every] || opts[:slice]
    248:         offset = 0
    249:         rows = []
    250:         while offset < values.length
    251:           rows << ds._import(columns, values[offset, slice_size], opts)
    252:           offset += slice_size
    253:         end
    254:         rows.flatten
    255:       else
    256:         ds._import(columns, values, opts)
    257:       end
    258:     end

insert(*values, &block)

Inserts values into the associated table. The returned value is generally the value of the primary key for the inserted row, but that is adapter dependent.

`insert` handles a number of different argument formats:

no arguments or single empty hash : | Uses DEFAULT VALUES
single hash : | Most common format, treats keys as columns an values as values
single array : | Treats entries as values, with no columns
two arrays : | Treats first array as columns, second array as values
single Dataset : | Treats as an insert based on a selection from the dataset given, with no columns
array and dataset : | Treats as an insert based on a selection from the dataset given, with the columns given by the array.

Examples:

      DB[:items].insert
      # INSERT INTO items DEFAULT VALUES

      DB[:items].insert({})
      # INSERT INTO items DEFAULT VALUES

      DB[:items].insert([1,2,3])
      # INSERT INTO items VALUES (1, 2, 3)

      DB[:items].insert([:a, :b], [1,2])
      # INSERT INTO items (a, b) VALUES (1, 2)

      DB[:items].insert(:a => 1, :b => 2)
      # INSERT INTO items (a, b) VALUES (1, 2)

      DB[:items].insert(DB[:old_items])
      # INSERT INTO items SELECT * FROM old_items

      DB[:items].insert([:a, :b], DB[:old_items])
      # INSERT INTO items (a, b) SELECT * FROM old_items

[Source]

         # File lib/sequel/dataset/actions.rb, line 295
    295:     def insert(*values, &block)
    296:       sql = insert_sql(*values)
    297:       if uses_returning?(:insert)
    298:         returning_fetch_rows(sql, &block)
    299:       else
    300:         execute_insert(sql)
    301:       end
    302:     end

insert_multiple(array, &block)

Inserts multiple values. If a block is given it is invoked for each item in the given array before inserting it. See `multi_insert` as a possibly faster version that may be able to insert multiple records in one SQL statement (if supported by the database). Returns an array of primary keys of inserted rows.

      DB[:table].insert_multiple([{:x=>1}, {:x=>2}])
      # => [4, 5]
      # INSERT INTO table (x) VALUES (1)
      # INSERT INTO table (x) VALUES (2)

      DB[:table].insert_multiple([{:x=>1}, {:x=>2}]){|row| row[:y] = row[:x] * 2}
      # => [6, 7]
      # INSERT INTO table (x, y) VALUES (1, 2)
      # INSERT INTO table (x, y) VALUES (2, 4)

[Source]

         # File lib/sequel/dataset/actions.rb, line 319
    319:     def insert_multiple(array, &block)
    320:       if block
    321:         array.map{|i| insert(block.call(i))}
    322:       else
    323:         array.map{|i| insert(i)}
    324:       end
    325:     end

interval(column)

Returns the interval between minimum and maximum values for the given column.

      DB[:table].interval(:id) # SELECT (max(id) - min(id)) FROM table LIMIT 1
      # => 6

[Source]

         # File lib/sequel/dataset/actions.rb, line 332
    332:     def interval(column)
    333:       aggregate_dataset.get{max(column) - min(column)}
    334:     end

last(*args, &block)

Reverses the order and then runs first with the given arguments and block. Note that this will not necessarily give you the last record in the dataset, unless you have an unambiguous order. If there is not currently an order for this dataset, raises an `Error`.

      DB[:table].order(:id).last # SELECT * FROM table ORDER BY id DESC LIMIT 1
      # => {:id=>10}

      DB[:table].order(:id.desc).last(2) # SELECT * FROM table ORDER BY id ASC LIMIT 2
      # => [{:id=>1}, {:id=>2}]

[Source]

         # File lib/sequel/dataset/actions.rb, line 346
    346:     def last(*args, &block)
    347:       raise(Error, 'No order specified') unless @opts[:order]
    348:       reverse.first(*args, &block)
    349:     end

map(column=nil, &block)

Maps column values for each record in the dataset (if a column name is given), or performs the stock mapping functionality of `Enumerable` otherwise. Raises an `Error` if both an argument and block are given.

      DB[:table].map(:id) # SELECT * FROM table
      # => [1, 2, 3, ...]

      DB[:table].map{|r| r[:id] * 2} # SELECT * FROM table
      # => [2, 4, 6, ...]

You can also provide an array of column names:

      DB[:table].map([:id, :name]) # SELECT * FROM table
      # => [[1, 'A'], [2, 'B'], [3, 'C'], ...]

[Source]

         # File lib/sequel/dataset/actions.rb, line 365
    365:     def map(column=nil, &block)
    366:       if column
    367:         raise(Error, ARG_BLOCK_ERROR_MSG) if block
    368:         return naked.map(column) if row_proc
    369:         if column.is_a?(Array)
    370:           super(){|r| r.values_at(*column)}
    371:         else
    372:           super(){|r| r[column]}
    373:         end
    374:       else
    375:         super(&block)
    376:       end
    377:     end

max(column)

Returns the maximum value for the given column.

      DB[:table].max(:id) # SELECT max(id) FROM table LIMIT 1
      # => 10

[Source]

         # File lib/sequel/dataset/actions.rb, line 383
    383:     def max(column)
    384:       aggregate_dataset.get{max(column)}
    385:     end

min(column)

Returns the minimum value for the given column.

      DB[:table].min(:id) # SELECT min(id) FROM table LIMIT 1
      # => 1

[Source]

         # File lib/sequel/dataset/actions.rb, line 391
    391:     def min(column)
    392:       aggregate_dataset.get{min(column)}
    393:     end

multi_insert(hashes, opts={})

This is a front end for import that allows you to submit an array of hashes instead of arrays of columns and values:

      DB[:table].multi_insert([{:x => 1}, {:x => 2}])
      # INSERT INTO table (x) VALUES (1)
      # INSERT INTO table (x) VALUES (2)

Be aware that all hashes should have the same keys if you use this calling method, otherwise some columns could be missed or set to null instead of to default values.

This respects the same options as import.

[Source]

         # File lib/sequel/dataset/actions.rb, line 407
    407:     def multi_insert(hashes, opts={})
    408:       return if hashes.empty?
    409:       columns = hashes.first.keys
    410:       import(columns, hashes.map{|h| columns.map{|c| h[c]}}, opts)
    411:     end

range(column)

Returns a `Range` instance made from the minimum and maximum values for the given column.

      DB[:table].range(:id) # SELECT max(id) AS v1, min(id) AS v2 FROM table LIMIT 1
      # => 1..10

[Source]

         # File lib/sequel/dataset/actions.rb, line 418
    418:     def range(column)
    419:       if r = aggregate_dataset.select{[min(column).as(v1), max(column).as(v2)]}.first
    420:         (r[:v1]..r[:v2])
    421:       end
    422:     end

select_hash(key_column, value_column)

Returns a hash with key_column values as keys and value_column values as values. Similar to to_hash, but only selects the two columns.

      DB[:table].select_hash(:id, :name) # SELECT id, name FROM table
      # => {1=>'a', 2=>'b', ...}

You can also provide an array of column names for either the key_column, the value column, or both:

      DB[:table].select_hash([:id, :foo], [:name, :bar]) # SELECT * FROM table
      # {[1, 3]=>['a', 'c'], [2, 4]=>['b', 'd'], ...}

When using this method, you must be sure that each expression has an alias that Sequel can determine. Usually you can do this by calling the as method on the expression and providing an alias.

[Source]

         # File lib/sequel/dataset/actions.rb, line 439
    439:     def select_hash(key_column, value_column)
    440:       if key_column.is_a?(Array)
    441:         if value_column.is_a?(Array)
    442:           select(*(key_column + value_column)).to_hash(key_column.map{|c| hash_key_symbol(c)}, value_column.map{|c| hash_key_symbol(c)})
    443:         else
    444:           select(*(key_column + [value_column])).to_hash(key_column.map{|c| hash_key_symbol(c)}, hash_key_symbol(value_column))
    445:         end
    446:       elsif value_column.is_a?(Array)
    447:         select(key_column, *value_column).to_hash(hash_key_symbol(key_column), value_column.map{|c| hash_key_symbol(c)})
    448:       else
    449:         select(key_column, value_column).to_hash(hash_key_symbol(key_column), hash_key_symbol(value_column))
    450:       end
    451:     end

select_map(column=nil, &block)

Selects the column given (either as an argument or as a block), and returns an array of all values of that column in the dataset. If you give a block argument that returns an array with multiple entries, the contents of the resulting array are undefined. Raises an Error if called with both an argument and a block.

      DB[:table].select_map(:id) # SELECT id FROM table
      # => [3, 5, 8, 1, ...]

      DB[:table].select_map{id * 2} # SELECT (id * 2) FROM table
      # => [6, 10, 16, 2, ...]

You can also provide an array of column names:

      DB[:table].select_map([:id, :name]) # SELECT id, name FROM table
      # => [[1, 'A'], [2, 'B'], [3, 'C'], ...]

If you provide an array of expressions, you must be sure that each entry in the array has an alias that Sequel can determine. Usually you can do this by calling the as method on the expression and providing an alias.

[Source]

         # File lib/sequel/dataset/actions.rb, line 473
    473:     def select_map(column=nil, &block)
    474:       _select_map(column, false, &block)
    475:     end

select_order_map(column=nil, &block)

The same as select_map, but in addition orders the array by the column.

      DB[:table].select_order_map(:id) # SELECT id FROM table ORDER BY id
      # => [1, 2, 3, 4, ...]

      DB[:table].select_order_map{id * 2} # SELECT (id * 2) FROM table ORDER BY (id * 2)
      # => [2, 4, 6, 8, ...]

You can also provide an array of column names:

      DB[:table].select_order_map([:id, :name]) # SELECT id, name FROM table ORDER BY id, name
      # => [[1, 'A'], [2, 'B'], [3, 'C'], ...]

If you provide an array of expressions, you must be sure that each entry in the array has an alias that Sequel can determine. Usually you can do this by calling the as method on the expression and providing an alias.

[Source]

         # File lib/sequel/dataset/actions.rb, line 494
    494:     def select_order_map(column=nil, &block)
    495:       _select_map(column, true, &block)
    496:     end

set(*args)

Alias for update, but not aliased directly so subclasses don‘t have to override both methods.

[Source]

         # File lib/sequel/dataset/actions.rb, line 500
    500:     def set(*args)
    501:       update(*args)
    502:     end

single_record()

Returns the first record in the dataset, or nil if the dataset has no records. Users should probably use `first` instead of this method.

[Source]

         # File lib/sequel/dataset/actions.rb, line 507
    507:     def single_record
    508:       clone(:limit=>1).each{|r| return r}
    509:       nil
    510:     end

single_value()

Returns the first value of the first record in the dataset. Returns nil if dataset is empty. Users should generally use `get` instead of this method.

[Source]

         # File lib/sequel/dataset/actions.rb, line 515
    515:     def single_value
    516:       if r = naked.ungraphed.single_record
    517:         r.values.first
    518:       end
    519:     end

sum(column)

Returns the sum for the given column.

      DB[:table].sum(:id) # SELECT sum(id) FROM table LIMIT 1
      # => 55

[Source]

         # File lib/sequel/dataset/actions.rb, line 525
    525:     def sum(column)
    526:       aggregate_dataset.get{sum(column)}
    527:     end

to_csv(include_column_titles = true)

Returns a string in CSV format containing the dataset records. By default the CSV representation includes the column titles in the first line. You can turn that off by passing false as the include_column_titles argument.

This does not use a CSV library or handle quoting of values in any way. If any values in any of the rows could include commas or line endings, you shouldn‘t use this.

      puts DB[:table].to_csv # SELECT * FROM table
      # id,name
      # 1,Jim
      # 2,Bob

[Source]

         # File lib/sequel/dataset/actions.rb, line 542
    542:     def to_csv(include_column_titles = true)
    543:       n = naked
    544:       cols = n.columns
    545:       csv = ''
    546:       csv << "#{cols.join(COMMA_SEPARATOR)}\r\n" if include_column_titles
    547:       n.each{|r| csv << "#{cols.collect{|c| r[c]}.join(COMMA_SEPARATOR)}\r\n"}
    548:       csv
    549:     end

to_hash(key_column, value_column = nil)

Returns a hash with one column used as key and another used as value. If rows have duplicate values for the key column, the latter row(s) will overwrite the value of the previous row(s). If the value_column is not given or nil, uses the entire hash as the value.

      DB[:table].to_hash(:id, :name) # SELECT * FROM table
      # {1=>'Jim', 2=>'Bob', ...}

      DB[:table].to_hash(:id) # SELECT * FROM table
      # {1=>{:id=>1, :name=>'Jim'}, 2=>{:id=>2, :name=>'Bob'}, ...}

You can also provide an array of column names for either the key_column, the value column, or both:

      DB[:table].to_hash([:id, :foo], [:name, :bar]) # SELECT * FROM table
      # {[1, 3]=>['Jim', 'bo'], [2, 4]=>['Bob', 'be'], ...}

      DB[:table].to_hash([:id, :name]) # SELECT * FROM table
      # {[1, 'Jim']=>{:id=>1, :name=>'Jim'}, [2, 'Bob'=>{:id=>2, :name=>'Bob'}, ...}

[Source]

         # File lib/sequel/dataset/actions.rb, line 570
    570:     def to_hash(key_column, value_column = nil)
    571:       h = {}
    572:       if value_column
    573:         return naked.to_hash(key_column, value_column) if row_proc
    574:         if value_column.is_a?(Array)
    575:           if key_column.is_a?(Array)
    576:             each{|r| h[r.values_at(*key_column)] = r.values_at(*value_column)}
    577:           else
    578:             each{|r| h[r[key_column]] = r.values_at(*value_column)}
    579:           end
    580:         else
    581:           if key_column.is_a?(Array)
    582:             each{|r| h[r.values_at(*key_column)] = r[value_column]}
    583:           else
    584:             each{|r| h[r[key_column]] = r[value_column]}
    585:           end
    586:         end
    587:       elsif key_column.is_a?(Array)
    588:         each{|r| h[r.values_at(*key_column)] = r}
    589:       else
    590:         each{|r| h[r[key_column]] = r}
    591:       end
    592:       h
    593:     end

truncate()

Truncates the dataset. Returns nil.

      DB[:table].truncate # TRUNCATE table
      # => nil

[Source]

         # File lib/sequel/dataset/actions.rb, line 599
    599:     def truncate
    600:       execute_ddl(truncate_sql)
    601:     end

update(values={}, &block)

Updates values for the dataset. The returned value is generally the number of rows updated, but that is adapter dependent. `values` should a hash where the keys are columns to set and values are the values to which to set the columns.

      DB[:table].update(:x=>nil) # UPDATE table SET x = NULL
      # => 10

      DB[:table].update(:x=>:x+1, :y=>0) # UPDATE table SET x = (x + 1), y = 0
      # => 10

[Source]

         # File lib/sequel/dataset/actions.rb, line 613
    613:     def update(values={}, &block)
    614:       sql = update_sql(values)
    615:       if uses_returning?(:update)
    616:         returning_fetch_rows(sql, &block)
    617:       else
    618:         execute_dui(sql)
    619:       end
    620:     end

### Protected Instance methods

_import(columns, values, opts)

Internals of import. If primary key values are requested, use separate insert commands for each row. Otherwise, call multi_insert_sql and execute each statement it gives separately.

[Source]

         # File lib/sequel/dataset/actions.rb, line 627
    627:     def _import(columns, values, opts)
    628:       trans_opts = opts.merge(:server=>@opts[:server])
    629:       if opts[:return] == :primary_key
    630:         @db.transaction(trans_opts){values.map{|v| insert(columns, v)}}
    631:       else
    632:         stmts = multi_insert_sql(columns, values)
    633:         @db.transaction(trans_opts){stmts.each{|st| execute_dui(st)}}
    634:       end
    635:     end

_select_map_multiple(ret_cols)

Return an array of arrays of values given by the symbols in ret_cols.

[Source]

         # File lib/sequel/dataset/actions.rb, line 638
    638:     def _select_map_multiple(ret_cols)
    639:       map{|r| r.values_at(*ret_cols)}
    640:     end

_select_map_single()

Returns an array of the first value in each row.

[Source]

         # File lib/sequel/dataset/actions.rb, line 643
    643:     def _select_map_single
    644:       map{|r| r.values.first}
    645:     end

## 4 - Methods that describe what the dataset supports

These methods all return booleans, with most describing whether or not the dataset supports a feature.

### Public Instance methods

provides_accurate_rows_matched?()

Whether this dataset will provide accurate number of rows matched for delete and update statements. Accurate in this case is the number of rows matched by the dataset‘s filter.

[Source]

        # File lib/sequel/dataset/features.rb, line 23
    23:     def provides_accurate_rows_matched?
    24:       true
    25:     end

quote_identifiers?()

Whether this dataset quotes identifiers.

[Source]

        # File lib/sequel/dataset/features.rb, line 10
    10:     def quote_identifiers?
    11:       if defined?(@quote_identifiers)
    12:         @quote_identifiers
    13:       elsif db.respond_to?(:quote_identifiers?)
    14:         @quote_identifiers = db.quote_identifiers?
    15:       else
    16:         @quote_identifiers = false
    17:       end
    18:     end

recursive_cte_requires_column_aliases?()

Whether you must use a column alias list for recursive CTEs (false by default).

[Source]

        # File lib/sequel/dataset/features.rb, line 29
    29:     def recursive_cte_requires_column_aliases?
    30:       false
    31:     end

requires_placeholder_type_specifiers?()

Whether type specifiers are required for prepared statement/bound variable argument placeholders (i.e. :bv__integer)

[Source]

        # File lib/sequel/dataset/features.rb, line 41
    41:     def requires_placeholder_type_specifiers?
    42:       false
    43:     end

requires_sql_standard_datetimes?()

Whether the dataset requires SQL standard datetimes (false by default, as most allow strings with ISO 8601 format).

[Source]

        # File lib/sequel/dataset/features.rb, line 35
    35:     def requires_sql_standard_datetimes?
    36:       false
    37:     end

supports_cte?(type=:select)

Whether the dataset supports common table expressions (the WITH clause). If given, `type` can be :select, :insert, :update, or :delete, in which case it determines whether WITH is supported for the respective statement type.

[Source]

        # File lib/sequel/dataset/features.rb, line 48
    48:     def supports_cte?(type=:select)
    49:       send("#{type}_clause_methods""#{type}_clause_methods").include?("#{type}_with_sql""#{type}_with_sql")
    50:     end

supports_cte_in_subqueries?()

Whether the dataset supports common table expressions (the WITH clause) in subqueries. If false, applies the WITH clause to the main query, which can cause issues if multiple WITH clauses use the same name.

[Source]

        # File lib/sequel/dataset/features.rb, line 55
    55:     def supports_cte_in_subqueries?
    56:       false
    57:     end

supports_distinct_on?()

Whether the dataset supports or can emulate the DISTINCT ON clause, false by default.

[Source]

        # File lib/sequel/dataset/features.rb, line 60
    60:     def supports_distinct_on?
    61:       false
    62:     end

supports_group_cube?()

Whether the dataset supports CUBE with GROUP BY.

[Source]

        # File lib/sequel/dataset/features.rb, line 65
    65:     def supports_group_cube?
    66:       false
    67:     end

supports_group_rollup?()

Whether the dataset supports ROLLUP with GROUP BY.

[Source]

        # File lib/sequel/dataset/features.rb, line 70
    70:     def supports_group_rollup?
    71:       false
    72:     end

supports_insert_select?()

Whether this dataset supports the `insert_select` method for returning all columns values directly from an insert query.

[Source]

        # File lib/sequel/dataset/features.rb, line 76
    76:     def supports_insert_select?
    77:       supports_returning?(:insert)
    78:     end

supports_intersect_except?()

Whether the dataset supports the INTERSECT and EXCEPT compound operations, true by default.

[Source]

        # File lib/sequel/dataset/features.rb, line 81
    81:     def supports_intersect_except?
    82:       true
    83:     end

supports_intersect_except_all?()

Whether the dataset supports the INTERSECT ALL and EXCEPT ALL compound operations, true by default.

[Source]

        # File lib/sequel/dataset/features.rb, line 86
    86:     def supports_intersect_except_all?
    87:       true
    88:     end

supports_is_true?()

Whether the dataset supports the IS TRUE syntax.

[Source]

        # File lib/sequel/dataset/features.rb, line 91
    91:     def supports_is_true?
    92:       true
    93:     end

supports_join_using?()

Whether the dataset supports the JOIN table USING (column1, …) syntax.

[Source]

        # File lib/sequel/dataset/features.rb, line 96
    96:     def supports_join_using?
    97:       true
    98:     end

supports_modifying_joins?()

Whether modifying joined datasets is supported.

[Source]

         # File lib/sequel/dataset/features.rb, line 101
    101:     def supports_modifying_joins?
    102:       false
    103:     end

supports_multiple_column_in?()

Whether the IN/NOT IN operators support multiple columns when an array of values is given.

[Source]

         # File lib/sequel/dataset/features.rb, line 107
    107:     def supports_multiple_column_in?
    108:       true
    109:     end

supports_ordered_distinct_on?()

Whether the dataset supports or can fully emulate the DISTINCT ON clause, including respecting the ORDER BY clause, false by default

[Source]

         # File lib/sequel/dataset/features.rb, line 113
    113:     def supports_ordered_distinct_on?
    114:       supports_distinct_on?
    115:     end

supports_returning?(type)

Whether the RETURNING clause is supported for the given type of query. `type` can be :insert, :update, or :delete.

[Source]

         # File lib/sequel/dataset/features.rb, line 119
    119:     def supports_returning?(type)
    120:       send("#{type}_clause_methods""#{type}_clause_methods").include?("#{type}_returning_sql""#{type}_returning_sql")
    121:     end

supports_select_all_and_column?()

Whether the database supports SELECT *, column FROM table

[Source]

         # File lib/sequel/dataset/features.rb, line 124
    124:     def supports_select_all_and_column?
    125:       true
    126:     end

supports_timestamp_timezones?()

Whether the dataset supports timezones in literal timestamps

[Source]

         # File lib/sequel/dataset/features.rb, line 129
    129:     def supports_timestamp_timezones?
    130:       false
    131:     end

supports_timestamp_usecs?()

Whether the dataset supports fractional seconds in literal timestamps

[Source]

         # File lib/sequel/dataset/features.rb, line 134
    134:     def supports_timestamp_usecs?
    135:       true
    136:     end

supports_where_true?()

Whether the dataset supports WHERE TRUE (or WHERE 1 for databases that that use 1 for true).

[Source]

         # File lib/sequel/dataset/features.rb, line 145
    145:     def supports_where_true?
    146:       true
    147:     end

supports_window_functions?()

Whether the dataset supports window functions.

[Source]

         # File lib/sequel/dataset/features.rb, line 139
    139:     def supports_window_functions?
    140:       false
    141:     end

## 5 - Methods related to dataset graphing

Dataset graphing changes the dataset to yield hashes where keys are table name symbols and values are hashes representing the columns related to that table. All of these methods return modified copies of the receiver.

### Public Instance methods

add_graph_aliases(graph_aliases)

Adds the given graph aliases to the list of graph aliases to use, unlike `set_graph_aliases`, which replaces the list (the equivalent of `select_more` when graphing). See `set_graph_aliases`.

      DB[:table].add_graph_aliases(:some_alias=>[:table, :column])
      # SELECT ..., table.column AS some_alias
      # => {:table=>{:column=>some_alias_value, ...}, ...}

[Source]

        # File lib/sequel/dataset/graph.rb, line 17
    17:     def add_graph_aliases(graph_aliases)
    18:       columns, graph_aliases = graph_alias_columns(graph_aliases)
    19:       ds = select_more(*columns)
    20:       ds.opts[:graph_aliases] = (ds.opts[:graph_aliases] || (ds.opts[:graph][:column_aliases] rescue {}) || {}).merge(graph_aliases)
    21:       ds
    22:     end

graph(dataset, join_conditions = nil, options = {}, &block)

Allows you to join multiple datasets/tables and have the result set split into component tables.

This differs from the usual usage of join, which returns the result set as a single hash. For example:

      # CREATE TABLE artists (id INTEGER, name TEXT);
      # CREATE TABLE albums (id INTEGER, name TEXT, artist_id INTEGER);

      DB[:artists].left_outer_join(:albums, :artist_id=>:id).first
      #=> {:id=>albums.id, :name=>albums.name, :artist_id=>albums.artist_id}

      DB[:artists].graph(:albums, :artist_id=>:id).first
      #=> {:artists=>{:id=>artists.id, :name=>artists.name}, :albums=>{:id=>albums.id, :name=>albums.name, :artist_id=>albums.artist_id}}

Using a join such as left_outer_join, the attribute names that are shared between the tables are combined in the single return hash. You can get around that by using `select` with correct aliases for all of the columns, but it is simpler to use `graph` and have the result set split for you. In addition, `graph` respects any `row_proc` of the current dataset and the datasets you use with `graph`.

If you are graphing a table and all columns for that table are nil, this indicates that no matching rows existed in the table, so graph will return nil instead of a hash with all nil values:

      # If the artist doesn't have any albums
      DB[:artists].graph(:albums, :artist_id=>:id).first
      => {:artists=>{:id=>artists.id, :name=>artists.name}, :albums=>nil}

Arguments:

dataset : | Can be a symbol (specifying a table), another dataset, or an object that responds to `dataset` and returns a symbol or a dataset
join_conditions : | Any condition(s) allowed by `join_table`.
block : | A block that is passed to `join_table`.

Options:

:from_self_alias : | The alias to use when the receiver is not a graphed dataset but it contains multiple FROM tables or a JOIN. In this case, the receiver is wrapped in a from_self before graphing, and this option determines the alias to use.
:implicit_qualifier : | The qualifier of implicit conditions, see join_table.
:join_type : | The type of join to use (passed to `join_table`). Defaults to :left_outer.
:select : | An array of columns to select. When not used, selects all columns in the given dataset. When set to false, selects no columns and is like simply joining the tables, though graph keeps some metadata about the join that makes it important to use `graph` instead of `join_table`.
:table_alias : | The alias to use for the table. If not specified, doesn‘t alias the table. You will get an error if the the alias (or table) name is used more than once.

[Source]

         # File lib/sequel/dataset/graph.rb, line 74
     74:     def graph(dataset, join_conditions = nil, options = {}, &block)
     75:       # Allow the use of a model, dataset, or symbol as the first argument
     76:       # Find the table name/dataset based on the argument
     77:       dataset = dataset.dataset if dataset.respond_to?(:dataset)
     78:       table_alias = options[:table_alias]
     79:       case dataset
     80:       when Symbol
     81:         table = dataset
     82:         dataset = @db[dataset]
     83:         table_alias ||= table
     84:       when ::Sequel::Dataset
     85:         if dataset.simple_select_all?
     86:           table = dataset.opts[:from].first
     87:           table_alias ||= table
     88:         else
     89:           table = dataset
     90:           table_alias ||= dataset_alias((@opts[:num_dataset_sources] || 0)+1)
     91:         end
     92:       else
     93:         raise Error, "The dataset argument should be a symbol, dataset, or model"
     94:       end
     95:
     96:       # Raise Sequel::Error with explanation that the table alias has been used
     97:       raise_alias_error = lambda do
     98:         raise(Error, "this #{options[:table_alias] ? 'alias' : 'table'} has already been been used, please specify " \
     99:           "#{options[:table_alias] ? 'a different alias' : 'an alias via the :table_alias option'}")
    100:       end
    101:
    102:       # Only allow table aliases that haven't been used
    103:       raise_alias_error.call if @opts[:graph] && @opts[:graph][:table_aliases] && @opts[:graph][:table_aliases].include?(table_alias)
    104:
    105:       # Use a from_self if this is already a joined table
    106:       ds = (!@opts[:graph] && (@opts[:from].length > 1 || @opts[:join])) ? from_self(:alias=>options[:from_self_alias] || first_source) : self
    107:
    108:       # Join the table early in order to avoid cloning the dataset twice
    109:       ds = ds.join_table(options[:join_type] || :left_outer, table, join_conditions, :table_alias=>table_alias, :implicit_qualifier=>options[:implicit_qualifier], &block)
    110:       opts = ds.opts
    111:
    112:       # Whether to include the table in the result set
    113:       add_table = options[:select] == false ? false : true
    114:       # Whether to add the columns to the list of column aliases
    115:       add_columns = !ds.opts.include?(:graph_aliases)
    116:
    117:       # Setup the initial graph data structure if it doesn't exist
    118:       if graph = opts[:graph]
    119:         opts[:graph] = graph = graph.dup
    120:         select = opts[:select].dup
    121:         [:column_aliases, :table_aliases, :column_alias_num].each{|k| graph[k] = graph[k].dup}
    122:       else
    123:         master = alias_symbol(ds.first_source_alias)
    124:         raise_alias_error.call if master == table_alias
    125:         # Master hash storing all .graph related information
    126:         graph = opts[:graph] = {}
    127:         # Associates column aliases back to tables and columns
    128:         column_aliases = graph[:column_aliases] = {}
    129:         # Associates table alias (the master is never aliased)
    130:         table_aliases = graph[:table_aliases] = {master=>self}
    131:         # Keep track of the alias numbers used
    132:         ca_num = graph[:column_alias_num] = Hash.new(0)
    133:         # All columns in the master table are never
    134:         # aliased, but are not included if set_graph_aliases
    135:         # has been used.
    136:         if add_columns
    137:           if (select = @opts[:select]) && !select.empty? && !(select.length == 1 && (select.first.is_a?(SQL::ColumnAll)))
    138:             select = select.each do |sel|
    139:               column = case sel
    140:               when Symbol
    141:                 _, c, a = split_symbol(sel)
    142:                 (a || c).to_sym
    143:               when SQL::Identifier
    144:                 sel.value.to_sym
    145:               when SQL::QualifiedIdentifier
    146:                 column = sel.column
    147:                 column = column.value if column.is_a?(SQL::Identifier)
    148:                 column.to_sym
    149:               when SQL::AliasedExpression
    150:                 column = sel.aliaz
    151:                 column = column.value if column.is_a?(SQL::Identifier)
    152:                 column.to_sym
    153:               else
    154:                 raise Error, "can't figure out alias to use for graphing for #{sel.inspect}"
    155:               end
    156:               column_aliases[column] = [master, column]
    157:             end
    158:             select = qualified_expression(select, master)
    159:           else
    160:             select = columns.map do |column|
    161:               column_aliases[column] = [master, column]
    162:               SQL::QualifiedIdentifier.new(master, column)
    163:             end
    164:           end
    165:         end
    166:       end
    167:
    168:       # Add the table alias to the list of aliases
    169:       # Even if it isn't been used in the result set,
    170:       # we add a key for it with a nil value so we can check if it
    171:       # is used more than once
    172:       table_aliases = graph[:table_aliases]
    173:       table_aliases[table_alias] = add_table ? dataset : nil
    174:
    175:       # Add the columns to the selection unless we are ignoring them
    176:       if add_table && add_columns
    177:         column_aliases = graph[:column_aliases]
    178:         ca_num = graph[:column_alias_num]
    179:         # Which columns to add to the result set
    180:         cols = options[:select] || dataset.columns
    181:         # If the column hasn't been used yet, don't alias it.
    182:         # If it has been used, try table_column.
    183:         # If that has been used, try table_column_N
    184:         # using the next value of N that we know hasn't been
    185:         # used
    186:         cols.each do |column|
    187:           col_alias, identifier = if column_aliases[column]
    188:             column_alias = "#{table_alias}_#{column}""#{table_alias}_#{column}"
    189:             if column_aliases[column_alias]
    190:               column_alias_num = ca_num[column_alias]
    191:               column_alias = "#{column_alias}_#{column_alias_num}""#{column_alias}_#{column_alias_num}"
    192:               ca_num[column_alias] += 1
    193:             end
    194:             [column_alias, SQL::AliasedExpression.new(SQL::QualifiedIdentifier.new(table_alias, column), column_alias)]
    195:           else
    196:             ident = SQL::QualifiedIdentifier.new(table_alias, column)
    197:             [column, ident]
    198:           end
    199:           column_aliases[col_alias] = [table_alias, column]
    200:           select.push(identifier)
    201:         end
    202:       end
    203:       add_columns ? ds.select(*select) : ds
    204:     end

set_graph_aliases(graph_aliases)

This allows you to manually specify the graph aliases to use when using graph. You can use it to only select certain columns, and have those columns mapped to specific aliases in the result set. This is the equivalent of `select` for a graphed dataset, and must be used instead of `select` whenever graphing is used.

graph_aliases :

Should be a hash with keys being symbols of column aliases, and values being either symbols or arrays with one to three elements. If the value is a symbol, it is assumed to be the same as a one element array containing that symbol. The first element of the array should be the table alias symbol. The second should be the actual column name symbol. If the array only has a single element the column name symbol will be assumed to be the same as the corresponding hash key. If the array has a third element, it is used as the value returned, instead of table_alias.column_name.

      DB[:artists].graph(:albums, :artist_id=>:id).
        set_graph_aliases(:name=>:artists,
                          :album_name=>[:albums, :name],
                          :forty_two=>[:albums, :fourtwo, 42]).first
      # SELECT artists.name, albums.name AS album_name, 42 AS forty_two ...
      # => {:artists=>{:name=>artists.name}, :albums=>{:name=>albums.name, :fourtwo=>42}}

[Source]

         # File lib/sequel/dataset/graph.rb, line 230
    230:     def set_graph_aliases(graph_aliases)
    231:       columns, graph_aliases = graph_alias_columns(graph_aliases)
    232:       ds = select(*columns)
    233:       ds.opts[:graph_aliases] = graph_aliases
    234:       ds
    235:     end

ungraphed()

Remove the splitting of results into subhashes, and all metadata related to the current graph (if any).

[Source]

         # File lib/sequel/dataset/graph.rb, line 239
    239:     def ungraphed
    240:       clone(:graph=>nil, :graph_aliases=>nil)
    241:     end

## 6 - Miscellaneous methods

These methods don‘t fit cleanly into another section.

### Constants

NOTIMPL_MSG | = | "This method must be overridden in Sequel adapters".freeze
ARRAY_ACCESS_ERROR_MSG | = | 'You cannot call Dataset#[] with an integer or with no arguments.'.freeze
ARG_BLOCK_ERROR_MSG | = | 'Must use either an argument or a block, not both'.freeze
IMPORT_ERROR_MSG | = | 'Using Sequel::Dataset#import an empty column array is not allowed'.freeze

### Attributes

db | [RW] | The database related to this dataset. This is the Database instance that will execute all of this dataset‘s queries.
opts | [RW] | The hash of options for this dataset, keys are symbols.

### Public Class methods

new(db, opts = nil)

Constructs a new Dataset instance with an associated database and options. Datasets are usually constructed by invoking the Database#[] method:

      DB[:posts]

Sequel::Dataset is an abstract class that is not useful by itself. Each database adapter provides a subclass of Sequel::Dataset, and has the Database#dataset method return an instance of that subclass.

[Source]

        # File lib/sequel/dataset/misc.rb, line 28
    28:     def initialize(db, opts = nil)
    29:       @db = db
    30:       @opts = opts || {}
    31:     end

### Public Instance methods

==(o)

Define a hash value such that datasets with the same DB, opts, and SQL will be consider equal.

[Source]

        # File lib/sequel/dataset/misc.rb, line 35
    35:     def ==(o)
    36:       o.is_a?(self.class) && db == o.db  && opts == o.opts && sql == o.sql
    37:     end

each_server() {|server(s)}| ...}

Yield a dataset for each server in the connection pool that is tied to that server. Intended for use in sharded environments where all servers need to be modified with the same data:

      DB[:configs].where(:key=>'setting').each_server{|ds| ds.update(:value=>'new_value')}

[Source]

        # File lib/sequel/dataset/misc.rb, line 49
    49:     def each_server
    50:       db.servers.each{|s| yield server(s)}
    51:     end

eql?(o)

Alias for ==

[Source]

        # File lib/sequel/dataset/misc.rb, line 40
    40:     def eql?(o)
    41:       self == o
    42:     end

first_source()

Alias of `first_source_alias`

[Source]

        # File lib/sequel/dataset/misc.rb, line 54
    54:     def first_source
    55:       first_source_alias
    56:     end

first_source_alias()

The first source (primary table) for this dataset. If the dataset doesn‘t have a table, raises an `Error`. If the table is aliased, returns the aliased name.

      DB[:table].first_source_alias
      # => :table

      DB[:table___t].first_source_alias
      # => :t

[Source]

        # File lib/sequel/dataset/misc.rb, line 66
    66:     def first_source_alias
    67:       source = @opts[:from]
    68:       if source.nil? || source.empty?
    69:         raise Error, 'No source specified for query'
    70:       end
    71:       case s = source.first
    72:       when SQL::AliasedExpression
    73:         s.aliaz
    74:       when Symbol
    75:         sch, table, aliaz = split_symbol(s)
    76:         aliaz ? aliaz.to_sym : s
    77:       else
    78:         s
    79:       end
    80:     end

first_source_table()

The first source (primary table) for this dataset. If the dataset doesn‘t have a table, raises an error. If the table is aliased, returns the original table, not the alias

      DB[:table].first_source_table
      # => :table

      DB[:table___t].first_source_table
      # => :table

[Source]

         # File lib/sequel/dataset/misc.rb, line 91
     91:     def first_source_table
     92:       source = @opts[:from]
     93:       if source.nil? || source.empty?
     94:         raise Error, 'No source specified for query'
     95:       end
     96:       case s = source.first
     97:       when SQL::AliasedExpression
     98:         s.expression
     99:       when Symbol
    100:         sch, table, aliaz = split_symbol(s)
    101:         aliaz ? (sch ? SQL::QualifiedIdentifier.new(sch, table) : table.to_sym) : s
    102:       else
    103:         s
    104:       end
    105:     end

hash()

Define a hash value such that datasets with the same DB, opts, and SQL will have the same hash value

[Source]

         # File lib/sequel/dataset/misc.rb, line 109
    109:     def hash
    110:       [db, opts.sort_by{|k, v| k.to_s}, sql].hash
    111:     end

identifier_input_method()

The String instance method to call on identifiers before sending them to the database.

[Source]

         # File lib/sequel/dataset/misc.rb, line 115
    115:     def identifier_input_method
    116:       if defined?(@identifier_input_method)
    117:         @identifier_input_method
    118:       elsif db.respond_to?(:identifier_input_method)
    119:         @identifier_input_method = db.identifier_input_method
    120:       else
    121:         @identifier_input_method = nil
    122:       end
    123:     end

identifier_output_method()

The String instance method to call on identifiers before sending them to the database.

[Source]

         # File lib/sequel/dataset/misc.rb, line 127
    127:     def identifier_output_method
    128:       if defined?(@identifier_output_method)
    129:         @identifier_output_method
    130:       elsif db.respond_to?(:identifier_output_method)
    131:         @identifier_output_method = db.identifier_output_method
    132:       else
    133:         @identifier_output_method = nil
    134:       end
    135:     end

inspect()

Returns a string representation of the dataset including the class name and the corresponding SQL select statement.

[Source]

         # File lib/sequel/dataset/misc.rb, line 139
    139:     def inspect
    140:       c = self.class
    141:       c = c.superclass while c.name.nil? || c.name == ''
    142:       "#<#{c.name}: #{sql.inspect}>"
    143:     end

row_number_column()

The alias to use for the row_number column, used when emulating OFFSET support and for eager limit strategies

[Source]

         # File lib/sequel/dataset/misc.rb, line 147
    147:     def row_number_column
    148:       :x_sequel_row_number_x
    149:     end

split_alias(c)

Splits a possible implicit alias in `c`, handling both SQL::AliasedExpressions and Symbols. Returns an array of two elements, with the first being the main expression, and the second being the alias.

[Source]

         # File lib/sequel/dataset/misc.rb, line 154
    154:     def split_alias(c)
    155:       case c
    156:       when Symbol
    157:         c_table, column, aliaz = split_symbol(c)
    158:         [c_table ? SQL::QualifiedIdentifier.new(c_table, column.to_sym) : column.to_sym, aliaz]
    159:       when SQL::AliasedExpression
    160:         [c.expression, c.aliaz]
    161:       when SQL::JoinClause
    162:         [c.table, c.table_alias]
    163:       else
    164:         [c, nil]
    165:       end
    166:     end

unused_table_alias(table_alias, used_aliases = [])

Creates a unique table alias that hasn‘t already been used in the dataset. table_alias can be any type of object accepted by alias_symbol. The symbol returned will be the implicit alias in the argument, possibly appended with "_N" if the implicit alias has already been used, where N is an integer starting at 0 and increasing until an unused one is found.

You can provide a second addition array argument containing symbols that should not be considered valid table aliases. The current aliases for the FROM and JOIN tables are automatically included in this array.

      DB[:table].unused_table_alias(:t)
      # => :t

      DB[:table].unused_table_alias(:table)
      # => :table_0

      DB[:table, :table_0].unused_table_alias(:table)
      # => :table_1

      DB[:table, :table_0].unused_table_alias(:table, [:table_1, :table_2])
      # => :table_3

[Source]

         # File lib/sequel/dataset/misc.rb, line 190
    190:     def unused_table_alias(table_alias, used_aliases = [])
    191:       table_alias = alias_symbol(table_alias)
    192:       used_aliases += opts[:from].map{|t| alias_symbol(t)} if opts[:from]
    193:       used_aliases += opts[:join].map{|j| j.table_alias ? alias_alias_symbol(j.table_alias) : alias_symbol(j.table)} if opts[:join]
    194:       if used_aliases.include?(table_alias)
    195:         i = 0
    196:         loop do
    197:           ta = "#{table_alias}_#{i}""#{table_alias}_#{i}"
    198:           return ta unless used_aliases.include?(ta)
    199:           i += 1
    200:         end
    201:       else
    202:         table_alias
    203:       end
    204:     end

## 8 - Methods related to prepared statements or bound variables

On some adapters, these use native prepared statements and bound variables, on others support is emulated. For details, see the "Prepared Statements/Bound Variables" guide.

### Classes and Modules

Module Sequel::Dataset::UnnumberedArgumentMapper

### Constants

PREPARED_ARG_PLACEHOLDER | = | LiteralString.new('?').freeze

### Public Instance methods

bind(bind_vars={})

Set the bind variables to use for the call. If bind variables have already been set for this dataset, they are updated with the contents of bind_vars.

      DB[:table].filter(:id=>:$id).bind(:id=>1).call(:first)
      # SELECT * FROM table WHERE id = ? LIMIT 1 -- (1)
      # => {:id=>1}

[Source]

         # File lib/sequel/dataset/prepared_statements.rb, line 211
    211:     def bind(bind_vars={})
    212:       clone(:bind_vars=>@opts[:bind_vars] ? @opts[:bind_vars].merge(bind_vars) : bind_vars)
    213:     end

call(type, bind_variables={}, *values, &block)

For the given type (:select, :first, :insert, :insert_select, :update, or :delete), run the sql with the bind variables specified in the hash. `values` is a hash passed to insert or update (if one of those types is used), which may contain placeholders.

      DB[:table].filter(:id=>:$id).call(:first, :id=>1)
      # SELECT * FROM table WHERE id = ? LIMIT 1 -- (1)
      # => {:id=>1}

[Source]

         # File lib/sequel/dataset/prepared_statements.rb, line 222
    222:     def call(type, bind_variables={}, *values, &block)
    223:       prepare(type, nil, *values).call(bind_variables, &block)
    224:     end

prepare(type, name=nil, *values)

Prepare an SQL statement for later execution. Takes a type similar to call, and the `name` symbol of the prepared statement. While `name` defaults to `nil`, it should always be provided as a symbol for the name of the prepared statement, as some databases require that prepared statements have names.

This returns a clone of the dataset extended with PreparedStatementMethods, which you can `call` with the hash of bind variables to use. The prepared statement is also stored in the associated database, where it can be called by name. The following usage is identical:

      ps = DB[:table].filter(:name=>:$name).prepare(:first, :select_by_name)

      ps.call(:name=>'Blah')
      # SELECT * FROM table WHERE name = ? -- ('Blah')
      # => {:id=>1, :name=>'Blah'}

      DB.call(:select_by_name, :name=>'Blah') # Same thing

[Source]

         # File lib/sequel/dataset/prepared_statements.rb, line 244
    244:     def prepare(type, name=nil, *values)
    245:       ps = to_prepared_statement(type, values)
    246:       db.prepared_statements[name] = ps if name
    247:       ps
    248:     end

### Protected Instance methods

to_prepared_statement(type, values=nil)

Return a cloned copy of the current dataset extended with PreparedStatementMethods, setting the type and modify values.

[Source]

         # File lib/sequel/dataset/prepared_statements.rb, line 254
    254:     def to_prepared_statement(type, values=nil)
    255:       ps = bind
    256:       ps.extend(PreparedStatementMethods)
    257:       ps.orig_dataset = self
    258:       ps.prepared_type = type
    259:       ps.prepared_modify_values = values
    260:       ps
    261:     end

## 1 - Methods that return modified datasets

These methods all return modified copies of the receiver.

### Constants

COLUMN_CHANGE_OPTS | = | [:select, :sql, :from, :join].freeze |  | The dataset options that require the removal of cached columns if changed.
NON_SQL_OPTIONS | = | [:server, :defaults, :overrides, :graph, :eager_graph, :graph_aliases] |  | Which options don‘t affect the SQL generation. Used by simple_select_all? to determine if this is a simple SELECT * FROM table.
CONDITIONED_JOIN_TYPES | = | [:inner, :full_outer, :right_outer, :left_outer, :full, :right, :left] |  | These symbols have _join methods created (e.g. inner_join) that call join_table with the symbol, passing along the arguments and block from the method call.
UNCONDITIONED_JOIN_TYPES | = | [:natural, :natural_left, :natural_right, :natural_full, :cross] |  | These symbols have _join methods created (e.g. natural_join) that call join_table with the symbol. They only accept a single table argument which is passed to join_table, and they raise an error if called with a block.
JOIN_METHODS | = | (CONDITIONED_JOIN_TYPES + UNCONDITIONED_JOIN_TYPES).map{|x| "#{x}_join".to_sym} + [:join, :join_table] |  | All methods that return modified datasets with a joined table added.

QUERY_METHODS

=

(<<-METHS).split.map{|x| x.to_sym} + JOIN_METHODS add_graph_aliases and distinct except exclude exclude_having exclude_where filter for_update from from_self graph grep group group_and_count group_by having intersect invert limit lock_style naked or order order_append order_by order_more order_prepend paginate qualify query reverse reverse_order select select_all select_append select_group select_more server set_defaults set_graph_aliases set_overrides unfiltered ungraphed ungrouped union unlimited unordered where with with_recursive with_sql METHS ).split.map{|x| x.to_sym} + JOIN_METHODS

Methods that return modified datasets

### Public Instance methods

and(*cond, &block)

Adds an further filter to an existing filter using AND. If no filter exists an error is raised. This method is identical to filter except it expects an existing filter.

      DB[:table].filter(:a).and(:b) # SELECT * FROM table WHERE a AND b

[Source]

        # File lib/sequel/dataset/query.rb, line 46
    46:     def and(*cond, &block)
    47:       raise(InvalidOperation, "No existing filter found.") unless @opts[:having] || @opts[:where]
    48:       filter(*cond, &block)
    49:     end

clone(opts = {})

Returns a new clone of the dataset with with the given options merged. If the options changed include options in COLUMN_CHANGE_OPTS, the cached columns are deleted. This method should generally not be called directly by user code.

[Source]

        # File lib/sequel/dataset/query.rb, line 55
    55:     def clone(opts = {})
    56:       c = super()
    57:       c.opts = @opts.merge(opts)
    58:       c.instance_variable_set(:@columns, nil) if opts.keys.any?{|o| COLUMN_CHANGE_OPTS.include?(o)}
    59:       c
    60:     end

distinct(*args)

Returns a copy of the dataset with the SQL DISTINCT clause. The DISTINCT clause is used to remove duplicate rows from the output. If arguments are provided, uses a DISTINCT ON clause, in which case it will only be distinct on those columns, instead of all returned columns. Raises an error if arguments are given and DISTINCT ON is not supported.

     DB[:items].distinct # SQL: SELECT DISTINCT * FROM items
     DB[:items].order(:id).distinct(:id) # SQL: SELECT DISTINCT ON (id) * FROM items ORDER BY id

[Source]

        # File lib/sequel/dataset/query.rb, line 71
    71:     def distinct(*args)
    72:       raise(InvalidOperation, "DISTINCT ON not supported") if !args.empty? && !supports_distinct_on?
    73:       clone(:distinct => args)
    74:     end

except(dataset, opts={})

Adds an EXCEPT clause using a second dataset object. An EXCEPT compound dataset returns all rows in the current dataset that are not in the given dataset. Raises an `InvalidOperation` if the operation is not supported. Options:

:alias : | Use the given value as the from_self alias
:all : | Set to true to use EXCEPT ALL instead of EXCEPT, so duplicate rows can occur
:from_self : | Set to false to not wrap the returned dataset in a from_self, use with care.

      DB[:items].except(DB[:other_items])
      # SELECT * FROM (SELECT * FROM items EXCEPT SELECT * FROM other_items) AS t1

      DB[:items].except(DB[:other_items], :all=>true, :from_self=>false)
      # SELECT * FROM items EXCEPT ALL SELECT * FROM other_items

      DB[:items].except(DB[:other_items], :alias=>:i)
      # SELECT * FROM (SELECT * FROM items EXCEPT SELECT * FROM other_items) AS i

[Source]

        # File lib/sequel/dataset/query.rb, line 93
    93:     def except(dataset, opts={})
    94:       opts = {:all=>opts} unless opts.is_a?(Hash)
    95:       raise(InvalidOperation, "EXCEPT not supported") unless supports_intersect_except?
    96:       raise(InvalidOperation, "EXCEPT ALL not supported") if opts[:all] && !supports_intersect_except_all?
    97:       compound_clone(:except, dataset, opts)
    98:     end

exclude(*cond, &block)

Performs the inverse of Dataset#filter. Note that if you have multiple filter conditions, this is not the same as a negation of all conditions.

      DB[:items].exclude(:category => 'software')
      # SELECT * FROM items WHERE (category != 'software')

      DB[:items].exclude(:category => 'software', :id=>3)
      # SELECT * FROM items WHERE ((category != 'software') OR (id != 3))

[Source]

         # File lib/sequel/dataset/query.rb, line 108
    108:     def exclude(*cond, &block)
    109:       _filter_or_exclude(true, @opts[:having] ? :having : :where, *cond, &block)
    110:     end

exclude_having(*cond, &block)

Inverts the given conditions and adds them to the HAVING clause.

      DB[:items].select_group(:name).exclude_having{count(name) < 2}
      # SELECT name FROM items GROUP BY name HAVING (count(name) >= 2)

[Source]

         # File lib/sequel/dataset/query.rb, line 116
    116:     def exclude_having(*cond, &block)
    117:       _filter_or_exclude(true, :having, *cond, &block)
    118:     end

exclude_where(*cond, &block)

Inverts the given conditions and adds them to the WHERE clause.

      DB[:items].select_group(:name).exclude_where(:category => 'software')
      # SELECT * FROM items WHERE (category != 'software')

      DB[:items].select_group(:name).
        exclude_having{count(name) < 2}.
        exclude_where(:category => 'software')
      # SELECT name FROM items WHERE (category != 'software')
      # GROUP BY name HAVING (count(name) >= 2)

[Source]

         # File lib/sequel/dataset/query.rb, line 130
    130:     def exclude_where(*cond, &block)
    131:       _filter_or_exclude(true, :where, *cond, &block)
    132:     end

filter(*cond, &block)

Returns a copy of the dataset with the given conditions imposed upon it. If the query already has a HAVING clause, then the conditions are imposed in the HAVING clause. If not, then they are imposed in the WHERE clause.

filter accepts the following argument types:

- Hash - list of equality/inclusion expressions
- Array - depends:
  - If first member is a string, assumes the rest of the arguments are parameters and interpolates them into the string.
  - If all members are arrays of length two, treats the same way as a hash, except it allows for duplicate keys to be specified.
  - Otherwise, treats each argument as a separate condition.
- String - taken literally
- Symbol - taken as a boolean column argument (e.g. WHERE active)
- Sequel::SQL::BooleanExpression - an existing condition expression, probably created using the Sequel expression filter DSL.

filter also takes a block, which should return one of the above argument types, and is treated the same way. This block yields a virtual row object, which is easy to use to create identifiers and functions. For more details on the virtual row support, see the "Virtual Rows" guide

If both a block and regular argument are provided, they get ANDed together.

Examples:

      DB[:items].filter(:id => 3)
      # SELECT * FROM items WHERE (id = 3)

      DB[:items].filter('price < ?', 100)
      # SELECT * FROM items WHERE price < 100

      DB[:items].filter([[:id, (1,2,3)], [:id, 0..10]])
      # SELECT * FROM items WHERE ((id IN (1, 2, 3)) AND ((id >= 0) AND (id <= 10)))

      DB[:items].filter('price < 100')
      # SELECT * FROM items WHERE price < 100

      DB[:items].filter(:active)
      # SELECT * FROM items WHERE :active

      DB[:items].filter{price < 100}
      # SELECT * FROM items WHERE (price < 100)

Multiple filter calls can be chained for scoping:

      software = dataset.filter(:category => 'software').filter{price < 100}
      # SELECT * FROM items WHERE ((category = 'software') AND (price < 100))

See the the "Dataset Filtering" guide for more examples and details.

[Source]

         # File lib/sequel/dataset/query.rb, line 186
    186:     def filter(*cond, &block)
    187:       _filter(@opts[:having] ? :having : :where, *cond, &block)
    188:     end

for_update()

Returns a cloned dataset with a :update lock style.

      DB[:table].for_update # SELECT * FROM table FOR UPDATE

[Source]

         # File lib/sequel/dataset/query.rb, line 193
    193:     def for_update
    194:       lock_style(:update)
    195:     end

from(*source)

Returns a copy of the dataset with the source changed. If no source is given, removes all tables. If multiple sources are given, it is the same as using a CROSS JOIN (cartesian product) between all tables.

      DB[:items].from # SQL: SELECT *
      DB[:items].from(:blah) # SQL: SELECT * FROM blah
      DB[:items].from(:blah, :foo) # SQL: SELECT * FROM blah, foo

[Source]

         # File lib/sequel/dataset/query.rb, line 204
    204:     def from(*source)
    205:       table_alias_num = 0
    206:       sources = []
    207:       ctes = nil
    208:       source.each do |s|
    209:         case s
    210:         when Hash
    211:           s.each{|k,v| sources << SQL::AliasedExpression.new(k,v)}
    212:         when Dataset
    213:           if hoist_cte?(s)
    214:             ctes ||= []
    215:             ctes += s.opts[:with]
    216:             s = s.clone(:with=>nil)
    217:           end
    218:           sources << SQL::AliasedExpression.new(s, dataset_alias(table_alias_num+=1))
    219:         when Symbol
    220:           sch, table, aliaz = split_symbol(s)
    221:           if aliaz
    222:             s = sch ? SQL::QualifiedIdentifier.new(sch, table) : SQL::Identifier.new(table)
    223:             sources << SQL::AliasedExpression.new(s, aliaz.to_sym)
    224:           else
    225:             sources << s
    226:           end
    227:         else
    228:           sources << s
    229:         end
    230:       end
    231:       o = {:from=>sources.empty? ? nil : sources}
    232:       o[:with] = (opts[:with] || []) + ctes if ctes
    233:       o[:num_dataset_sources] = table_alias_num if table_alias_num > 0
    234:       clone(o)
    235:     end

from_self(opts={})

Returns a dataset selecting from the current dataset. Supplying the :alias option controls the alias of the result.

      ds = DB[:items].order(:name).select(:id, :name)
      # SELECT id,name FROM items ORDER BY name

      ds.from_self
      # SELECT * FROM (SELECT id, name FROM items ORDER BY name) AS t1

      ds.from_self(:alias=>:foo)
      # SELECT * FROM (SELECT id, name FROM items ORDER BY name) AS foo

[Source]

         # File lib/sequel/dataset/query.rb, line 248
    248:     def from_self(opts={})
    249:       fs = {}
    250:       @opts.keys.each{|k| fs[k] = nil unless NON_SQL_OPTIONS.include?(k)}
    251:       clone(fs).from(opts[:alias] ? as(opts[:alias]) : self)
    252:     end

grep(columns, patterns, opts={})

Match any of the columns to any of the patterns. The terms can be strings (which use LIKE) or regular expressions (which are only supported on MySQL and PostgreSQL). Note that the total number of pattern matches will be Array(columns).length * Array(terms).length, which could cause performance issues.

Options (all are boolean):

:all_columns : | All columns must be matched to any of the given patterns.
:all_patterns : | All patterns must match at least one of the columns.
:case_insensitive : | Use a case insensitive pattern match (the default is case sensitive if the database supports it).

If both :all_columns and :all_patterns are true, all columns must match all patterns.

Examples:

      dataset.grep(:a, '%test%')
      # SELECT * FROM items WHERE (a LIKE '%test%')

      dataset.grep([:a, :b], %w'%test% foo')
      # SELECT * FROM items WHERE ((a LIKE '%test%') OR (a LIKE 'foo') OR (b LIKE '%test%') OR (b LIKE 'foo'))

      dataset.grep([:a, :b], %w'%foo% %bar%', :all_patterns=>true)
      # SELECT * FROM a WHERE (((a LIKE '%foo%') OR (b LIKE '%foo%')) AND ((a LIKE '%bar%') OR (b LIKE '%bar%')))

      dataset.grep([:a, :b], %w'%foo% %bar%', :all_columns=>true)
      # SELECT * FROM a WHERE (((a LIKE '%foo%') OR (a LIKE '%bar%')) AND ((b LIKE '%foo%') OR (b LIKE '%bar%')))

      dataset.grep([:a, :b], %w'%foo% %bar%', :all_patterns=>true, :all_columns=>true)
      # SELECT * FROM a WHERE ((a LIKE '%foo%') AND (b LIKE '%foo%') AND (a LIKE '%bar%') AND (b LIKE '%bar%'))

[Source]

         # File lib/sequel/dataset/query.rb, line 285
    285:     def grep(columns, patterns, opts={})
    286:       if opts[:all_patterns]
    287:         conds = Array(patterns).map do |pat|
    288:           SQL::BooleanExpression.new(opts[:all_columns] ? :AND : :OR, *Array(columns).map{|c| SQL::StringExpression.like(c, pat, opts)})
    289:         end
    290:         filter(SQL::BooleanExpression.new(opts[:all_patterns] ? :AND : :OR, *conds))
    291:       else
    292:         conds = Array(columns).map do |c|
    293:           SQL::BooleanExpression.new(:OR, *Array(patterns).map{|pat| SQL::StringExpression.like(c, pat, opts)})
    294:         end
    295:         filter(SQL::BooleanExpression.new(opts[:all_columns] ? :AND : :OR, *conds))
    296:       end
    297:     end

group(*columns, &block)

Returns a copy of the dataset with the results grouped by the value of the given columns. If a block is given, it is treated as a virtual row block, similar to `filter`.

      DB[:items].group(:id) # SELECT * FROM items GROUP BY id
      DB[:items].group(:id, :name) # SELECT * FROM items GROUP BY id, name
      DB[:items].group{[a, sum(b)]} # SELECT * FROM items GROUP BY a, sum(b)

[Source]

         # File lib/sequel/dataset/query.rb, line 306
    306:     def group(*columns, &block)
    307:       virtual_row_columns(columns, block)
    308:       clone(:group => (columns.compact.empty? ? nil : columns))
    309:     end

group_and_count(*columns, &block)

Returns a dataset grouped by the given column with count by group. Column aliases may be supplied, and will be included in the select clause. If a block is given, it is treated as a virtual row block, similar to `filter`.

Examples:

      DB[:items].group_and_count(:name).all
      # SELECT name, count(*) AS count FROM items GROUP BY name
      # => [{:name=>'a', :count=>1}, ...]

      DB[:items].group_and_count(:first_name, :last_name).all
      # SELECT first_name, last_name, count(*) AS count FROM items GROUP BY first_name, last_name
      # => [{:first_name=>'a', :last_name=>'b', :count=>1}, ...]

      DB[:items].group_and_count(:first_name___name).all
      # SELECT first_name AS name, count(*) AS count FROM items GROUP BY first_name
      # => [{:name=>'a', :count=>1}, ...]

      DB[:items].group_and_count{substr(first_name, 1, 1).as(initial)}.all
      # SELECT substr(first_name, 1, 1) AS initial, count(*) AS count FROM items GROUP BY substr(first_name, 1, 1)
      # => [{:initial=>'a', :count=>1}, ...]

[Source]

         # File lib/sequel/dataset/query.rb, line 337
    337:     def group_and_count(*columns, &block)
    338:       select_group(*columns, &block).select_more(COUNT_OF_ALL_AS_COUNT)
    339:     end

group_by(*columns, &block)

Alias of group

[Source]

         # File lib/sequel/dataset/query.rb, line 312
    312:     def group_by(*columns, &block)
    313:       group(*columns, &block)
    314:     end

group_cube()

Adds the appropriate CUBE syntax to GROUP BY.

[Source]

         # File lib/sequel/dataset/query.rb, line 342
    342:     def group_cube
    343:       raise Error, "GROUP BY CUBE not supported on #{db.database_type}" unless supports_group_cube?
    344:       clone(:group_options=>:cube)
    345:     end

group_rollup()

Adds the appropriate ROLLUP syntax to GROUP BY.

[Source]

         # File lib/sequel/dataset/query.rb, line 348
    348:     def group_rollup
    349:       raise Error, "GROUP BY ROLLUP not supported on #{db.database_type}" unless supports_group_rollup?
    350:       clone(:group_options=>:rollup)
    351:     end

having(*cond, &block)

Returns a copy of the dataset with the HAVING conditions changed. See filter for argument types.

      DB[:items].group(:sum).having(:sum=>10)
      # SELECT * FROM items GROUP BY sum HAVING (sum = 10)

[Source]

         # File lib/sequel/dataset/query.rb, line 357
    357:     def having(*cond, &block)
    358:       _filter(:having, *cond, &block)
    359:     end

intersect(dataset, opts={})

Adds an INTERSECT clause using a second dataset object. An INTERSECT compound dataset returns all rows in both the current dataset and the given dataset. Raises an `InvalidOperation` if the operation is not supported. Options:

:alias : | Use the given value as the from_self alias
:all : | Set to true to use INTERSECT ALL instead of INTERSECT, so duplicate rows can occur
:from_self : | Set to false to not wrap the returned dataset in a from_self, use with care.

      DB[:items].intersect(DB[:other_items])
      # SELECT * FROM (SELECT * FROM items INTERSECT SELECT * FROM other_items) AS t1

      DB[:items].intersect(DB[:other_items], :all=>true, :from_self=>false)
      # SELECT * FROM items INTERSECT ALL SELECT * FROM other_items

      DB[:items].intersect(DB[:other_items], :alias=>:i)
      # SELECT * FROM (SELECT * FROM items INTERSECT SELECT * FROM other_items) AS i

[Source]

         # File lib/sequel/dataset/query.rb, line 378
    378:     def intersect(dataset, opts={})
    379:       opts = {:all=>opts} unless opts.is_a?(Hash)
    380:       raise(InvalidOperation, "INTERSECT not supported") unless supports_intersect_except?
    381:       raise(InvalidOperation, "INTERSECT ALL not supported") if opts[:all] && !supports_intersect_except_all?
    382:       compound_clone(:intersect, dataset, opts)
    383:     end

invert()

Inverts the current filter.

      DB[:items].filter(:category => 'software').invert
      # SELECT * FROM items WHERE (category != 'software')

      DB[:items].filter(:category => 'software', :id=>3).invert
      # SELECT * FROM items WHERE ((category != 'software') OR (id != 3))

[Source]

         # File lib/sequel/dataset/query.rb, line 392
    392:     def invert
    393:       having, where = @opts[:having], @opts[:where]
    394:       raise(Error, "No current filter") unless having || where
    395:       o = {}
    396:       o[:having] = SQL::BooleanExpression.invert(having) if having
    397:       o[:where] = SQL::BooleanExpression.invert(where) if where
    398:       clone(o)
    399:     end

join(*args, &block)

Alias of `inner_join`

[Source]

         # File lib/sequel/dataset/query.rb, line 402
    402:     def join(*args, &block)
    403:       inner_join(*args, &block)
    404:     end

join_table(type, table, expr=nil, options={}) {|table_name, last_alias, @opts[:join] || []| ...}

Returns a joined dataset. Not usually called directly, users should use the appropriate join method (e.g. join, left_join, natural_join, cross_join) which fills in the `type` argument.

Takes the following arguments:

- type - The type of join to do (e.g. :inner)
- table - Depends on type:
  - Dataset - a subselect is performed with an alias of tN for some value of N
  - Model (or anything responding to :table_name) - table.table_name
  - String, Symbol: table
- expr - specifies conditions, depends on type:
  - Hash, Array of two element arrays - Assumes key (1st arg) is column of joined table (unless already qualified), and value (2nd arg) is column of the last joined or primary table (or the :implicit_qualifier option). To specify multiple conditions on a single joined table column, you must use an array. Uses a JOIN with an ON clause.
  - Array - If all members of the array are symbols, considers them as columns and uses a JOIN with a USING clause. Most databases will remove duplicate columns from the result set if this is used.
  - nil - If a block is not given, doesn‘t use ON or USING, so the JOIN should be a NATURAL or CROSS join. If a block is given, uses an ON clause based on the block, see below.
  - Everything else - pretty much the same as a using the argument in a call to filter, so strings are considered literal, symbols specify boolean columns, and Sequel expressions can be used. Uses a JOIN with an ON clause.
- options - a hash of options, with any of the following keys:
  - :table_alias - the name of the table‘s alias when joining, necessary for joining to the same table more than once. No alias is used by default.
  - :implicit_qualifier - The name to use for qualifying implicit conditions. By default, the last joined or primary table is used.
- block - The block argument should only be given if a JOIN with an ON clause is used, in which case it yields the table alias/name for the table currently being joined, the table alias/name for the last joined (or first table), and an array of previous SQL::JoinClause. Unlike `filter`, this block is not treated as a virtual row block.

Examples:

      DB[:a].join_table(:cross, :b)
      # SELECT * FROM a CROSS JOIN b

      DB[:a].join_table(:inner, DB[:b], :c=>d)
      # SELECT * FROM a INNER JOIN (SELECT * FROM b) AS t1 ON (t1.c = a.d)

      DB[:a].join_table(:left, :b___c, [:d])
      # SELECT * FROM a LEFT JOIN b AS c USING (d)

      DB[:a].natural_join(:b).join_table(:inner, :c) do |ta, jta, js|
        (:d.qualify(ta) > :e.qualify(jta)) & {:f.qualify(ta)=>DB.from(js.first.table).select(:g)}
      end
      # SELECT * FROM a NATURAL JOIN b INNER JOIN c
      #   ON ((c.d > b.e) AND (c.f IN (SELECT g FROM b)))

[Source]

         # File lib/sequel/dataset/query.rb, line 457
    457:     def join_table(type, table, expr=nil, options={}, &block)
    458:       if hoist_cte?(table)
    459:         s, ds = hoist_cte(table)
    460:         return s.join_table(type, ds, expr, options, &block)
    461:       end
    462:
    463:       using_join = expr.is_a?(Array) && !expr.empty? && expr.all?{|x| x.is_a?(Symbol)}
    464:       if using_join && !supports_join_using?
    465:         h = {}
    466:         expr.each{|s| h[s] = s}
    467:         return join_table(type, table, h, options)
    468:       end
    469:
    470:       case options
    471:       when Hash
    472:         table_alias = options[:table_alias]
    473:         last_alias = options[:implicit_qualifier]
    474:       when Symbol, String, SQL::Identifier
    475:         table_alias = options
    476:         last_alias = nil
    477:       else
    478:         raise Error, "invalid options format for join_table: #{options.inspect}"
    479:       end
    480:
    481:       if Dataset === table
    482:         if table_alias.nil?
    483:           table_alias_num = (@opts[:num_dataset_sources] || 0) + 1
    484:           table_alias = dataset_alias(table_alias_num)
    485:         end
    486:         table_name = table_alias
    487:       else
    488:         table = table.table_name if table.respond_to?(:table_name)
    489:         table, implicit_table_alias = split_alias(table)
    490:         table_alias ||= implicit_table_alias
    491:         table_name = table_alias || table
    492:       end
    493:
    494:       join = if expr.nil? and !block
    495:         SQL::JoinClause.new(type, table, table_alias)
    496:       elsif using_join
    497:         raise(Sequel::Error, "can't use a block if providing an array of symbols as expr") if block
    498:         SQL::JoinUsingClause.new(expr, type, table, table_alias)
    499:       else
    500:         last_alias ||= @opts[:last_joined_table] || first_source_alias
    501:         if Sequel.condition_specifier?(expr)
    502:           expr = expr.collect do |k, v|
    503:             k = qualified_column_name(k, table_name) if k.is_a?(Symbol)
    504:             v = qualified_column_name(v, last_alias) if v.is_a?(Symbol)
    505:             [k,v]
    506:           end
    507:           expr = SQL::BooleanExpression.from_value_pairs(expr)
    508:         end
    509:         if block
    510:           expr2 = yield(table_name, last_alias, @opts[:join] || [])
    511:           expr = expr ? SQL::BooleanExpression.new(:AND, expr, expr2) : expr2
    512:         end
    513:         SQL::JoinOnClause.new(expr, type, table, table_alias)
    514:       end
    515:
    516:       opts = {:join => (@opts[:join] || []) + [join], :last_joined_table => table_name}
    517:       opts[:num_dataset_sources] = table_alias_num if table_alias_num
    518:       clone(opts)
    519:     end

limit(l, o = nil)

If given an integer, the dataset will contain only the first l results. If given a range, it will contain only those at offsets within that range. If a second argument is given, it is used as an offset. To use an offset without a limit, pass nil as the first argument.

      DB[:items].limit(10) # SELECT * FROM items LIMIT 10
      DB[:items].limit(10, 20) # SELECT * FROM items LIMIT 10 OFFSET 20
      DB[:items].limit(10...20) # SELECT * FROM items LIMIT 10 OFFSET 10
      DB[:items].limit(10..20) # SELECT * FROM items LIMIT 11 OFFSET 10
      DB[:items].limit(nil, 20) # SELECT * FROM items OFFSET 20

[Source]

         # File lib/sequel/dataset/query.rb, line 538
    538:     def limit(l, o = nil)
    539:       return from_self.limit(l, o) if @opts[:sql]
    540:
    541:       if Range === l
    542:         o = l.first
    543:         l = l.last - l.first + (l.exclude_end? ? 0 : 1)
    544:       end
    545:       l = l.to_i if l.is_a?(String) && !l.is_a?(LiteralString)
    546:       if l.is_a?(Integer)
    547:         raise(Error, 'Limits must be greater than or equal to 1') unless l >= 1
    548:       end
    549:       opts = {:limit => l}
    550:       if o
    551:         o = o.to_i if o.is_a?(String) && !o.is_a?(LiteralString)
    552:         if o.is_a?(Integer)
    553:           raise(Error, 'Offsets must be greater than or equal to 0') unless o >= 0
    554:         end
    555:         opts[:offset] = o
    556:       end
    557:       clone(opts)
    558:     end

lock_style(style)

Returns a cloned dataset with the given lock style. If style is a string, it will be used directly. Otherwise, a symbol may be used for database independent locking. Currently :update is respected by most databases, and :share is supported by some.

      DB[:items].lock_style('FOR SHARE') # SELECT * FROM items FOR SHARE

[Source]

         # File lib/sequel/dataset/query.rb, line 566
    566:     def lock_style(style)
    567:       clone(:lock => style)
    568:     end

naked()

Returns a cloned dataset without a row_proc.

      ds = DB[:items]
      ds.row_proc = proc{|r| r.invert}
      ds.all # => [{2=>:id}]
      ds.naked.all # => [{:id=>2}]

[Source]

         # File lib/sequel/dataset/query.rb, line 576
    576:     def naked
    577:       ds = clone
    578:       ds.row_proc = nil
    579:       ds
    580:     end

or(*cond, &block)

Adds an alternate filter to an existing filter using OR. If no filter exists an `Error` is raised.

      DB[:items].filter(:a).or(:b) # SELECT * FROM items WHERE a OR b

[Source]

         # File lib/sequel/dataset/query.rb, line 586
    586:     def or(*cond, &block)
    587:       clause = (@opts[:having] ? :having : :where)
    588:       raise(InvalidOperation, "No existing filter found.") unless @opts[clause]
    589:       cond = cond.first if cond.size == 1
    590:       clone(clause => SQL::BooleanExpression.new(:OR, @opts[clause], filter_expr(cond, &block)))
    591:     end

order(*columns, &block)

Returns a copy of the dataset with the order changed. If the dataset has an existing order, it is ignored and overwritten with this order. If a nil is given the returned dataset has no order. This can accept multiple arguments of varying kinds, such as SQL functions. If a block is given, it is treated as a virtual row block, similar to `filter`.

      DB[:items].order(:name) # SELECT * FROM items ORDER BY name
      DB[:items].order(:a, :b) # SELECT * FROM items ORDER BY a, b
      DB[:items].order('a + b'.lit) # SELECT * FROM items ORDER BY a + b
      DB[:items].order(:a + :b) # SELECT * FROM items ORDER BY (a + b)
      DB[:items].order(:name.desc) # SELECT * FROM items ORDER BY name DESC
      DB[:items].order(:name.asc(:nulls=>:last)) # SELECT * FROM items ORDER BY name ASC NULLS LAST
      DB[:items].order{sum(name).desc} # SELECT * FROM items ORDER BY sum(name) DESC
      DB[:items].order(nil) # SELECT * FROM items

[Source]

         # File lib/sequel/dataset/query.rb, line 607
    607:     def order(*columns, &block)
    608:       virtual_row_columns(columns, block)
    609:       clone(:order => (columns.compact.empty?) ? nil : columns)
    610:     end

order_append(*columns, &block)

Alias of order_more, for naming consistency with order_prepend.

[Source]

         # File lib/sequel/dataset/query.rb, line 613
    613:     def order_append(*columns, &block)
    614:       order_more(*columns, &block)
    615:     end

order_by(*columns, &block)

Alias of order

[Source]

         # File lib/sequel/dataset/query.rb, line 618
    618:     def order_by(*columns, &block)
    619:       order(*columns, &block)
    620:     end

order_more(*columns, &block)

Returns a copy of the dataset with the order columns added to the end of the existing order.

      DB[:items].order(:a).order(:b) # SELECT * FROM items ORDER BY b
      DB[:items].order(:a).order_more(:b) # SELECT * FROM items ORDER BY a, b

[Source]

         # File lib/sequel/dataset/query.rb, line 627
    627:     def order_more(*columns, &block)
    628:       columns = @opts[:order] + columns if @opts[:order]
    629:       order(*columns, &block)
    630:     end

order_prepend(*columns, &block)

Returns a copy of the dataset with the order columns added to the beginning of the existing order.

      DB[:items].order(:a).order(:b) # SELECT * FROM items ORDER BY b
      DB[:items].order(:a).order_prepend(:b) # SELECT * FROM items ORDER BY b, a

[Source]

         # File lib/sequel/dataset/query.rb, line 637
    637:     def order_prepend(*columns, &block)
    638:       ds = order(*columns, &block)
    639:       @opts[:order] ? ds.order_more(*@opts[:order]) : ds
    640:     end

qualify(table=first_source)

Qualify to the given table, or first source if no table is given.

      DB[:items].filter(:id=>1).qualify
      # SELECT items.* FROM items WHERE (items.id = 1)

      DB[:items].filter(:id=>1).qualify(:i)
      # SELECT i.* FROM items WHERE (i.id = 1)

[Source]

         # File lib/sequel/dataset/query.rb, line 649
    649:     def qualify(table=first_source)
    650:       qualify_to(table)
    651:     end

qualify_to(table)

Return a copy of the dataset with unqualified identifiers in the SELECT, WHERE, GROUP, HAVING, and ORDER clauses qualified by the given table. If no columns are currently selected, select all columns of the given table.

      DB[:items].filter(:id=>1).qualify_to(:i)
      # SELECT i.* FROM items WHERE (i.id = 1)

[Source]

         # File lib/sequel/dataset/query.rb, line 660
    660:     def qualify_to(table)
    661:       o = @opts
    662:       return clone if o[:sql]
    663:       h = {}
    664:       (o.keys & QUALIFY_KEYS).each do |k|
    665:         h[k] = qualified_expression(o[k], table)
    666:       end
    667:       h[:select] = [SQL::ColumnAll.new(table)] if !o[:select] || o[:select].empty?
    668:       clone(h)
    669:     end

qualify_to_first_source()

Qualify the dataset to its current first source. This is useful if you have unqualified identifiers in the query that all refer to the first source, and you want to join to another table which has columns with the same name as columns in the current dataset. See `qualify_to`.

      DB[:items].filter(:id=>1).qualify_to_first_source
      # SELECT items.* FROM items WHERE (items.id = 1)

[Source]

         # File lib/sequel/dataset/query.rb, line 679
    679:     def qualify_to_first_source
    680:       qualify_to(first_source)
    681:     end

returning(*values)

Modify the RETURNING clause, only supported on a few databases. If returning is used, instead of insert returning the autogenerated primary key or update/delete returning the number of modified rows, results are returned using `fetch_rows`.

      DB[:items].returning # RETURNING *
      DB[:items].returning(nil) # RETURNING NULL
      DB[:items].returning(:id, :name) # RETURNING id, name

[Source]

         # File lib/sequel/dataset/query.rb, line 691
    691:     def returning(*values)
    692:       clone(:returning=>values)
    693:     end

reverse(*order)

Returns a copy of the dataset with the order reversed. If no order is given, the existing order is inverted.

      DB[:items].reverse(:id) # SELECT * FROM items ORDER BY id DESC
      DB[:items].order(:id).reverse # SELECT * FROM items ORDER BY id DESC
      DB[:items].order(:id).reverse(:name.asc) # SELECT * FROM items ORDER BY name ASC

[Source]

         # File lib/sequel/dataset/query.rb, line 701
    701:     def reverse(*order)
    702:       order(*invert_order(order.empty? ? @opts[:order] : order))
    703:     end

reverse_order(*order)

Alias of `reverse`

[Source]

         # File lib/sequel/dataset/query.rb, line 706
    706:     def reverse_order(*order)
    707:       reverse(*order)
    708:     end

select(*columns, &block)

Returns a copy of the dataset with the columns selected changed to the given columns. This also takes a virtual row block, similar to `filter`.

      DB[:items].select(:a) # SELECT a FROM items
      DB[:items].select(:a, :b) # SELECT a, b FROM items
      DB[:items].select{[a, sum(b)]} # SELECT a, sum(b) FROM items

[Source]

         # File lib/sequel/dataset/query.rb, line 717
    717:     def select(*columns, &block)
    718:       virtual_row_columns(columns, block)
    719:       m = []
    720:       columns.each do |i|
    721:         i.is_a?(Hash) ? m.concat(i.map{|k, v| SQL::AliasedExpression.new(k,v)}) : m << i
    722:       end
    723:       clone(:select => m)
    724:     end

select_all(*tables)

Returns a copy of the dataset selecting the wildcard if no arguments are given. If arguments are given, treat them as tables and select all columns (using the wildcard) from each table.

      DB[:items].select(:a).select_all # SELECT * FROM items
      DB[:items].select_all(:items) # SELECT items.* FROM items
      DB[:items].select_all(:items, :foo) # SELECT items.*, foo.* FROM items

[Source]

         # File lib/sequel/dataset/query.rb, line 733
    733:     def select_all(*tables)
    734:       if tables.empty?
    735:         clone(:select => nil)
    736:       else
    737:         select(*tables.map{|t| i, a = split_alias(t); a || i}.map{|t| SQL::ColumnAll.new(t)})
    738:       end
    739:     end

select_append(*columns, &block)

Returns a copy of the dataset with the given columns added to the existing selected columns. If no columns are currently selected, it will select the columns given in addition to *.

      DB[:items].select(:a).select(:b) # SELECT b FROM items
      DB[:items].select(:a).select_append(:b) # SELECT a, b FROM items
      DB[:items].select_append(:b) # SELECT *, b FROM items

[Source]

         # File lib/sequel/dataset/query.rb, line 748
    748:     def select_append(*columns, &block)
    749:       cur_sel = @opts[:select]
    750:       if !cur_sel || cur_sel.empty?
    751:         unless supports_select_all_and_column?
    752:           return select_all(*(Array(@opts[:from]) + Array(@opts[:join]))).select_more(*columns, &block)
    753:         end
    754:         cur_sel = [WILDCARD]
    755:       end
    756:       select(*(cur_sel + columns), &block)
    757:     end

select_group(*columns, &block)

Set both the select and group clauses with the given `columns`. Column aliases may be supplied, and will be included in the select clause. This also takes a virtual row block similar to `filter`.

      DB[:items].select_group(:a, :b)
      # SELECT a, b FROM items GROUP BY a, b

      DB[:items].select_group(:c___a){f(c2)}
      # SELECT c AS a, f(c2) FROM items GROUP BY c, f(c2)

[Source]

         # File lib/sequel/dataset/query.rb, line 768
    768:     def select_group(*columns, &block)
    769:       virtual_row_columns(columns, block)
    770:       select(*columns).group(*columns.map{|c| unaliased_identifier(c)})
    771:     end

select_more(*columns, &block)

Returns a copy of the dataset with the given columns added to the existing selected columns. If no columns are currently selected it will just select the columns given.

      DB[:items].select(:a).select(:b) # SELECT b FROM items
      DB[:items].select(:a).select_more(:b) # SELECT a, b FROM items
      DB[:items].select_more(:b) # SELECT b FROM items

[Source]

         # File lib/sequel/dataset/query.rb, line 780
    780:     def select_more(*columns, &block)
    781:       columns = @opts[:select] + columns if @opts[:select]
    782:       select(*columns, &block)
    783:     end

server(servr)

Set the server for this dataset to use. Used to pick a specific database shard to run a query against, or to override the default (where SELECT uses :read_only database and all other queries use the :default database). This method is always available but is only useful when database sharding is being used.

      DB[:items].all # Uses the :read_only or :default server
      DB[:items].delete # Uses the :default server
      DB[:items].server(:blah).delete # Uses the :blah server

[Source]

         # File lib/sequel/dataset/query.rb, line 794
    794:     def server(servr)
    795:       clone(:server=>servr)
    796:     end

set_defaults(hash)

Set the default values for insert and update statements. The values hash passed to insert or update are merged into this hash, so any values in the hash passed to insert or update will override values passed to this method.

      DB[:items].set_defaults(:a=>'a', :c=>'c').insert(:a=>'d', :b=>'b')
      # INSERT INTO items (a, c, b) VALUES ('d', 'c', 'b')

[Source]

         # File lib/sequel/dataset/query.rb, line 804
    804:     def set_defaults(hash)
    805:       clone(:defaults=>(@opts[:defaults]||{}).merge(hash))
    806:     end

set_overrides(hash)

Set values that override hash arguments given to insert and update statements. This hash is merged into the hash provided to insert or update, so values will override any values given in the insert/update hashes.

      DB[:items].set_overrides(:a=>'a', :c=>'c').insert(:a=>'d', :b=>'b')
      # INSERT INTO items (a, c, b) VALUES ('a', 'c', 'b')

[Source]

         # File lib/sequel/dataset/query.rb, line 814
    814:     def set_overrides(hash)
    815:       clone(:overrides=>hash.merge(@opts[:overrides]||{}))
    816:     end

unbind()

Unbind bound variables from this dataset‘s filter and return an array of two objects. The first object is a modified dataset where the filter has been replaced with one that uses bound variable placeholders. The second object is the hash of unbound variables. You can then prepare and execute (or just call) the dataset with the bound variables to get results.

      ds, bv = DB[:items].filter(:a=>1).unbind
      ds # SELECT * FROM items WHERE (a = $a)
      bv #  {:a => 1}
      ds.call(:select, bv)

[Source]

         # File lib/sequel/dataset/query.rb, line 828
    828:     def unbind
    829:       u = Unbinder.new
    830:       ds = clone(:where=>u.transform(opts[:where]), :join=>u.transform(opts[:join]))
    831:       [ds, u.binds]
    832:     end

unfiltered()

Returns a copy of the dataset with no filters (HAVING or WHERE clause) applied.

      DB[:items].group(:a).having(:a=>1).where(:b).unfiltered
      # SELECT * FROM items GROUP BY a

[Source]

         # File lib/sequel/dataset/query.rb, line 838
    838:     def unfiltered
    839:       clone(:where => nil, :having => nil)
    840:     end

ungrouped()

Returns a copy of the dataset with no grouping (GROUP or HAVING clause) applied.

      DB[:items].group(:a).having(:a=>1).where(:b).ungrouped
      # SELECT * FROM items WHERE b

[Source]

         # File lib/sequel/dataset/query.rb, line 846
    846:     def ungrouped
    847:       clone(:group => nil, :having => nil)
    848:     end

union(dataset, opts={})

Adds a UNION clause using a second dataset object. A UNION compound dataset returns all rows in either the current dataset or the given dataset. Options:

:alias : | Use the given value as the from_self alias
:all : | Set to true to use UNION ALL instead of UNION, so duplicate rows can occur
:from_self : | Set to false to not wrap the returned dataset in a from_self, use with care.

      DB[:items].union(DB[:other_items])
      # SELECT * FROM (SELECT * FROM items UNION SELECT * FROM other_items) AS t1

      DB[:items].union(DB[:other_items], :all=>true, :from_self=>false)
      # SELECT * FROM items UNION ALL SELECT * FROM other_items

      DB[:items].union(DB[:other_items], :alias=>:i)
      # SELECT * FROM (SELECT * FROM items UNION SELECT * FROM other_items) AS i

[Source]

         # File lib/sequel/dataset/query.rb, line 866
    866:     def union(dataset, opts={})
    867:       opts = {:all=>opts} unless opts.is_a?(Hash)
    868:       compound_clone(:union, dataset, opts)
    869:     end

unlimited()

Returns a copy of the dataset with no limit or offset.

      DB[:items].limit(10, 20).unlimited # SELECT * FROM items

[Source]

         # File lib/sequel/dataset/query.rb, line 874
    874:     def unlimited
    875:       clone(:limit=>nil, :offset=>nil)
    876:     end

unordered()

Returns a copy of the dataset with no order.

      DB[:items].order(:a).unordered # SELECT * FROM items

[Source]

         # File lib/sequel/dataset/query.rb, line 881
    881:     def unordered
    882:       order(nil)
    883:     end

where(*cond, &block)

Add a condition to the WHERE clause. See `filter` for argument types.

      DB[:items].group(:a).having(:a).filter(:b)
      # SELECT * FROM items GROUP BY a HAVING a AND b

      DB[:items].group(:a).having(:a).where(:b)
      # SELECT * FROM items WHERE b GROUP BY a HAVING a

[Source]

         # File lib/sequel/dataset/query.rb, line 892
    892:     def where(*cond, &block)
    893:       _filter(:where, *cond, &block)
    894:     end

with(name, dataset, opts={})

Add a common table expression (CTE) with the given name and a dataset that defines the CTE. A common table expression acts as an inline view for the query. Options:

:args : | Specify the arguments/columns for the CTE, should be an array of symbols.
:recursive : | Specify that this is a recursive CTE

      DB[:items].with(:items, DB[:syx].filter(:name.like('A%')))
      # WITH items AS (SELECT * FROM syx WHERE (name LIKE 'A%')) SELECT * FROM items

[Source]

         # File lib/sequel/dataset/query.rb, line 904
    904:     def with(name, dataset, opts={})
    905:       raise(Error, 'This datatset does not support common table expressions') unless supports_cte?
    906:       if hoist_cte?(dataset)
    907:         s, ds = hoist_cte(dataset)
    908:         s.with(name, ds, opts)
    909:       else
    910:         clone(:with=>(@opts[:with]||[]) + [opts.merge(:name=>name, :dataset=>dataset)])
    911:       end
    912:     end

with_recursive(name, nonrecursive, recursive, opts={})

Add a recursive common table expression (CTE) with the given name, a dataset that defines the nonrecursive part of the CTE, and a dataset that defines the recursive part of the CTE. Options:

:args : | Specify the arguments/columns for the CTE, should be an array of symbols.
:union_all : | Set to false to use UNION instead of UNION ALL combining the nonrecursive and recursive parts.

      DB[:t].select(:i___id, :pi___parent_id).
       with_recursive(:t,
                      DB[:i1].filter(:parent_id=>nil),
                      DB[:t].join(:t, :i=>:parent_id).select(:i1__id, :i1__parent_id),
                      :args=>[:i, :pi])
      # WITH RECURSIVE t(i, pi) AS (
      #   SELECT * FROM i1 WHERE (parent_id IS NULL)
      #   UNION ALL
      #   SELECT i1.id, i1.parent_id FROM t INNER JOIN t ON (t.i = t.parent_id)
      # )
      # SELECT i AS id, pi AS parent_id FROM t

[Source]

         # File lib/sequel/dataset/query.rb, line 931
    931:     def with_recursive(name, nonrecursive, recursive, opts={})
    932:       raise(Error, 'This datatset does not support common table expressions') unless supports_cte?
    933:       if hoist_cte?(nonrecursive)
    934:         s, ds = hoist_cte(nonrecursive)
    935:         s.with_recursive(name, ds, recursive, opts)
    936:       elsif hoist_cte?(recursive)
    937:         s, ds = hoist_cte(recursive)
    938:         s.with_recursive(name, nonrecursive, ds, opts)
    939:       else
    940:         clone(:with=>(@opts[:with]||[]) + [opts.merge(:recursive=>true, :name=>name, :dataset=>nonrecursive.union(recursive, {:all=>opts[:union_all] != false, :from_self=>false}))])
    941:       end
    942:     end

with_sql(sql, *args)

Returns a copy of the dataset with the static SQL used. This is useful if you want to keep the same row_proc/graph, but change the SQL used to custom SQL.

      DB[:items].with_sql('SELECT * FROM foo') # SELECT * FROM foo

You can use placeholders in your SQL and provide arguments for those placeholders:

      DB[:items].with_sql('SELECT ? FROM foo', 1) # SELECT 1 FROM foo

You can also provide a method name and arguments to call to get the SQL:

      DB[:items].with_sql(:insert_sql, :b=>1) # INSERT INTO items (b) VALUES (1)

[Source]

         # File lib/sequel/dataset/query.rb, line 956
    956:     def with_sql(sql, *args)
    957:       if sql.is_a?(Symbol)
    958:         sql = send(sql, *args)
    959:       else
    960:         sql = SQL::PlaceholderLiteralString.new(sql, args) unless args.empty?
    961:       end
    962:       clone(:sql=>sql)
    963:     end

### Protected Instance methods

compound_clone(type, dataset, opts)

Add the dataset to the list of compounds

[Source]

         # File lib/sequel/dataset/query.rb, line 968
    968:     def compound_clone(type, dataset, opts)
    969:       if hoist_cte?(dataset)
    970:         s, ds = hoist_cte(dataset)
    971:         return s.compound_clone(type, ds, opts)
    972:       end
    973:       ds = compound_from_self.clone(:compounds=>Array(@opts[:compounds]).map{|x| x.dup} + [[type, dataset.compound_from_self, opts[:all]]])
    974:       opts[:from_self] == false ? ds : ds.from_self(opts)
    975:     end

options_overlap(opts)

Return true if the dataset has a non-nil value for any key in opts.

[Source]

         # File lib/sequel/dataset/query.rb, line 978
    978:     def options_overlap(opts)
    979:       !(@opts.collect{|k,v| k unless v.nil?}.compact & opts).empty?
    980:     end

simple_select_all?()

Whether this dataset is a simple SELECT * FROM table.

[Source]

         # File lib/sequel/dataset/query.rb, line 983
    983:     def simple_select_all?
    984:       o = @opts.reject{|k,v| v.nil? || NON_SQL_OPTIONS.include?(k)}
    985:       o.length == 1 && (f = o[:from]) && f.length == 1 && (f.first.is_a?(Symbol) || f.first.is_a?(SQL::AliasedExpression))
    986:     end

## 3 - User Methods relating to SQL Creation

These are methods you can call to see what SQL will be generated by the dataset.

### Public Instance methods

delete_sql()

Returns a DELETE SQL query string. See `delete`.

      dataset.filter{|o| o.price >= 100}.delete_sql
      # => "DELETE FROM items WHERE (price >= 100)"

[Source]

        # File lib/sequel/dataset/sql.rb, line 12
    12:     def delete_sql
    13:       return static_sql(opts[:sql]) if opts[:sql]
    14:       check_modification_allowed!
    15:       clause_sql(:delete)
    16:     end

exists()

Returns an EXISTS clause for the dataset as a `LiteralString`.

      DB.select(1).where(DB[:items].exists)
      # SELECT 1 WHERE (EXISTS (SELECT * FROM items))

[Source]

        # File lib/sequel/dataset/sql.rb, line 22
    22:     def exists
    23:       SQL::PlaceholderLiteralString.new("EXISTS ?", [self], true)
    24:     end

insert_sql(*values)

Returns an INSERT SQL query string. See `insert`.

      DB[:items].insert_sql(:a=>1)
      # => "INSERT INTO items (a) VALUES (1)"

[Source]

        # File lib/sequel/dataset/sql.rb, line 30
    30:     def insert_sql(*values)
    31:       return static_sql(@opts[:sql]) if @opts[:sql]
    32:
    33:       check_modification_allowed!
    34:
    35:       columns = []
    36:
    37:       case values.size
    38:       when 0
    39:         return insert_sql({})
    40:       when 1
    41:         case vals = values.at(0)
    42:         when Hash
    43:           vals = @opts[:defaults].merge(vals) if @opts[:defaults]
    44:           vals = vals.merge(@opts[:overrides]) if @opts[:overrides]
    45:           values = []
    46:           vals.each do |k,v|
    47:             columns << k
    48:             values << v
    49:           end
    50:         when Dataset, Array, LiteralString
    51:           values = vals
    52:         else
    53:           if vals.respond_to?(:values) && (v = vals.values).is_a?(Hash)
    54:             return insert_sql(v)
    55:           end
    56:         end
    57:       when 2
    58:         if (v0 = values.at(0)).is_a?(Array) && ((v1 = values.at(1)).is_a?(Array) || v1.is_a?(Dataset) || v1.is_a?(LiteralString))
    59:           columns, values = v0, v1
    60:           raise(Error, "Different number of values and columns given to insert_sql") if values.is_a?(Array) and columns.length != values.length
    61:         end
    62:       end
    63:
    64:       if values.is_a?(Array) && values.empty? && !insert_supports_empty_values?
    65:         columns = [columns().last]
    66:         values = ['DEFAULT'.lit]
    67:       end
    68:       clone(:columns=>columns, :values=>values)._insert_sql
    69:     end

literal_append(sql, v)

Returns a literal representation of a value to be used as part of an SQL expression.

      DB[:items].literal("abc'def\\") #=> "'abc''def\\\\'"
      DB[:items].literal(:items__id) #=> "items.id"
      DB[:items].literal([1, 2, 3]) => "(1, 2, 3)"
      DB[:items].literal(DB[:items]) => "(SELECT * FROM items)"
      DB[:items].literal(:x + 1 > :y) => "((x + 1) > y)"

If an unsupported object is given, an `Error` is raised.

[Source]

         # File lib/sequel/dataset/sql.rb, line 81
     81:     def literal_append(sql, v)
     82:       case v
     83:       when Symbol
     84:         literal_symbol_append(sql, v)
     85:       when String
     86:         case v
     87:         when LiteralString
     88:           sql << v
     89:         when SQL::Blob
     90:           literal_blob_append(sql, v)
     91:         else
     92:           literal_string_append(sql, v)
     93:         end
     94:       when Integer
     95:         sql << literal_integer(v)
     96:       when Hash
     97:         literal_hash_append(sql, v)
     98:       when SQL::Expression
     99:         literal_expression_append(sql, v)
    100:       when Float
    101:         sql << literal_float(v)
    102:       when BigDecimal
    103:         sql << literal_big_decimal(v)
    104:       when NilClass
    105:         sql << literal_nil
    106:       when TrueClass
    107:         sql << literal_true
    108:       when FalseClass
    109:         sql << literal_false
    110:       when Array
    111:         literal_array_append(sql, v)
    112:       when Time
    113:         sql << (v.is_a?(SQLTime) ? literal_sqltime(v) : literal_time(v))
    114:       when DateTime
    115:         sql << literal_datetime(v)
    116:       when Date
    117:         sql << literal_date(v)
    118:       when Dataset
    119:         literal_dataset_append(sql, v)
    120:       else
    121:         literal_other_append(sql, v)
    122:       end
    123:     end

multi_insert_sql(columns, values)

Returns an array of insert statements for inserting multiple records. This method is used by `multi_insert` to format insert statements and expects a keys array and and an array of value arrays.

This method should be overridden by descendants if the support inserting multiple records in a single SQL statement.

[Source]

         # File lib/sequel/dataset/sql.rb, line 131
    131:     def multi_insert_sql(columns, values)
    132:       values.map{|r| insert_sql(columns, r)}
    133:     end

select_sql()

Returns a SELECT SQL query string.

      dataset.select_sql # => "SELECT * FROM items"

[Source]

         # File lib/sequel/dataset/sql.rb, line 138
    138:     def select_sql
    139:       return static_sql(@opts[:sql]) if @opts[:sql]
    140:       clause_sql(:select)
    141:     end

sql()

Same as `select_sql`, not aliased directly to make subclassing simpler.

[Source]

         # File lib/sequel/dataset/sql.rb, line 144
    144:     def sql
    145:       select_sql
    146:     end

truncate_sql()

Returns a TRUNCATE SQL query string. See `truncate`

      DB[:items].truncate_sql # => 'TRUNCATE items'

[Source]

         # File lib/sequel/dataset/sql.rb, line 151
    151:     def truncate_sql
    152:       if opts[:sql]
    153:         static_sql(opts[:sql])
    154:       else
    155:         check_modification_allowed!
    156:         raise(InvalidOperation, "Can't truncate filtered datasets") if opts[:where]
    157:         _truncate_sql(source_list(opts[:from]))
    158:       end
    159:     end

update_sql(values = {})

Formats an UPDATE statement using the given values. See `update`.

      DB[:items].update_sql(:price => 100, :category => 'software')
      # => "UPDATE items SET price = 100, category = 'software'

Raises an `Error` if the dataset is grouped or includes more than one table.

[Source]

         # File lib/sequel/dataset/sql.rb, line 168
    168:     def update_sql(values = {})
    169:       return static_sql(opts[:sql]) if opts[:sql]
    170:       check_modification_allowed!
    171:       clone(:values=>values)._update_sql
    172:     end

## 9 - Internal Methods relating to SQL Creation

These methods, while public, are not designed to be used directly by the end user.

### Constants

ALL | = | ' ALL'.freeze
AND_SEPARATOR | = | " AND ".freeze
APOS | = | "'".freeze
APOS_RE | = | /'/.freeze
ARRAY_EMPTY | = | '(NULL)'.freeze
AS | = | ' AS '.freeze
ASC | = | ' ASC'.freeze
BACKSLASH_RE | = | /\\/.freeze
BOOL_FALSE | = | "'f'".freeze
BOOL_TRUE | = | "'t'".freeze
BRACKET_CLOSE | = | ']'.freeze
BRACKET_OPEN | = | '['.freeze
CASE_ELSE | = | " ELSE ".freeze
CASE_END | = | " END)".freeze
CASE_OPEN | = | '(CASE'.freeze
CASE_THEN | = | " THEN ".freeze
CASE_WHEN | = | " WHEN ".freeze
CAST_OPEN | = | 'CAST('.freeze
COLUMN_ALL | = | '.*'.freeze
COLUMN_REF_RE1 | = | /\A((?:(?!__).)+)__((?:(?!___).)+)___(.+)\z/.freeze
COLUMN_REF_RE2 | = | /\A((?:(?!___).)+)___(.+)\z/.freeze
COLUMN_REF_RE3 | = | /\A((?:(?!__).)+)__(.+)\z/.freeze
COMMA | = | ', '.freeze
COMMA_SEPARATOR | = | COMMA
CONDITION_FALSE | = | '(1 = 0)'.freeze
CONDITION_TRUE | = | '(1 = 1)'.freeze
COUNT_FROM_SELF_OPTS | = | [:distinct, :group, :sql, :limit, :compounds]
COUNT_OF_ALL_AS_COUNT | = | SQL::Function.new(:count, LiteralString.new('*'.freeze)).as(:count)
DATASET_ALIAS_BASE_NAME | = | 't'.freeze
DEFAULT_VALUES | = | " DEFAULT VALUES".freeze
DELETE | = | 'DELETE'.freeze
DELETE_CLAUSE_METHODS | = | clause_methods(:delete, %w'delete from where')
DESC | = | ' DESC'.freeze
DISTINCT | = | " DISTINCT".freeze
DOT | = | '.'.freeze
DOUBLE_APOS | = | "''".freeze
DOUBLE_QUOTE | = | '""'.freeze
EQUAL | = | ' = '.freeze
EXTRACT | = | 'extract('.freeze
FOR_UPDATE | = | ' FOR UPDATE'.freeze
FORMAT_DATE | = | "'%Y-%m-%d'".freeze
FORMAT_DATE_STANDARD | = | "DATE '%Y-%m-%d'".freeze
FORMAT_OFFSET | = | "%+03i%02i".freeze
FORMAT_TIMESTAMP_RE | = | /%[Nz]/.freeze
FORMAT_TIMESTAMP_USEC | = | ".%06d".freeze
FORMAT_USEC | = | '%N'.freeze
FRAME_ALL | = | "ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING".freeze
FRAME_ROWS | = | "ROWS BETWEEN UNBOUNDED PRECEDING AND CURRENT ROW".freeze
FROM | = | ' FROM '.freeze
FUNCTION_EMPTY | = | '()'.freeze
GROUP_BY | = | " GROUP BY ".freeze
HAVING | = | " HAVING ".freeze
INSERT | = | "INSERT".freeze
INSERT_CLAUSE_METHODS | = | clause_methods(:insert, %w'insert into columns values')
INTO | = | " INTO ".freeze
IS_LITERALS | = | {nil=>'NULL'.freeze, true=>'TRUE'.freeze, false=>'FALSE'.freeze}.freeze
IS_OPERATORS | = | ::Sequel::SQL::ComplexExpression::IS_OPERATORS
LIMIT | = | " LIMIT ".freeze
N_ARITY_OPERATORS | = | ::Sequel::SQL::ComplexExpression::N_ARITY_OPERATORS
NOT_SPACE | = | 'NOT '.freeze
NULL | = | "NULL".freeze
NULLS_FIRST | = | " NULLS FIRST".freeze
NULLS_LAST | = | " NULLS LAST".freeze
OFFSET | = | " OFFSET ".freeze
ON | = | ' ON '.freeze
ON_PAREN | = | " ON (".freeze
ORDER_BY | = | " ORDER BY ".freeze
ORDER_BY_NS | = | "ORDER BY ".freeze
OVER | = | ' OVER '.freeze
PAREN_CLOSE | = | ')'.freeze
PAREN_OPEN | = | '('.freeze
PAREN_SPACE_OPEN | = | ' ('.freeze
PARTITION_BY | = | "PARTITION BY ".freeze
QUAD_BACKSLASH | = | "\\\\\\\\".freeze
QUALIFY_KEYS | = | [:select, :where, :having, :order, :group]
QUESTION_MARK | = | '?'.freeze
QUESTION_MARK_RE | = | /\?/.freeze
QUOTE | = | '"'.freeze
QUOTE_RE | = | /"/.freeze
RETURNING | = | " RETURNING ".freeze
SELECT | = | 'SELECT'.freeze
SELECT_CLAUSE_METHODS | = | clause_methods(:select, %w'with select distinct columns from join where group having compounds order limit lock')
SET | = | ' SET '.freeze
SPACE | = | ' '.freeze
SQL_WITH | = | "WITH ".freeze
TILDE | = | '~'.freeze
TIMESTAMP_FORMAT | = | "'%Y-%m-%d %H:%M:%S%N%z'".freeze
STANDARD_TIMESTAMP_FORMAT | = | "TIMESTAMP #{TIMESTAMP_FORMAT}".freeze
TWO_ARITY_OPERATORS | = | ::Sequel::SQL::ComplexExpression::TWO_ARITY_OPERATORS
UNDERSCORE | = | '_'.freeze
UPDATE | = | 'UPDATE'.freeze
UPDATE_CLAUSE_METHODS | = | clause_methods(:update, %w'update table set where')
USING | = | ' USING ('.freeze
VALUES | = | " VALUES ".freeze
WHERE | = | " WHERE ".freeze
WILDCARD | = | LiteralString.new('*').freeze

PUBLIC_APPEND_METHODS

=

(<<-END).split.map{|x| x.to_sym} literal aliased_expression_sql array_sql boolean_constant_sql case_expression_sql cast_sql column_all_sql complex_expression_sql constant_sql function_sql join_clause_sql join_on_clause_sql join_using_clause_sql negative_boolean_constant_sql ordered_expression_sql placeholder_literal_string_sql qualified_identifier_sql quote_identifier quote_schema_table quoted_identifier subscript_sql window_sql window_function_sql END ).split.map{|x| x.to_sym}

PRIVATE_APPEND_METHODS | = | (<<-END).split.map{|x| x.to_sym} argument_list as_sql column_list compound_dataset_sql expression_list literal_array literal_blob literal_dataset literal_expression literal_hash literal_other literal_string literal_symbol source_list subselect_sql table_ref END ).split.map{|x| x.to_sym}

### Public Class methods

clause_methods(type, clauses)

Given a type (e.g. select) and an array of clauses, return an array of methods to call to build the SQL string.

[Source]

         # File lib/sequel/dataset/sql.rb, line 181
    181:     def self.clause_methods(type, clauses)
    182:       clauses.map{|clause| "#{type}_#{clause}_sql""#{type}_#{clause}_sql"}.freeze
    183:     end

def_append_methods(meths)

[Source]

         # File lib/sequel/dataset/sql.rb, line 327
    327:     def self.def_append_methods(meths)
    328:       meths.each do |meth|
    329:         class_eval("def \#{meth}(*args, &block)\ns = ''\n\#{meth}_append(s, *args, &block)\ns\nend\n", __FILE__, __LINE__ + 1)
    330:       end
    331:     end

### Public Instance methods

aliased_expression_sql_append(sql, ae)

SQL fragment for AliasedExpression

[Source]

         # File lib/sequel/dataset/sql.rb, line 343
    343:     def aliased_expression_sql_append(sql, ae)
    344:       literal_append(sql, ae.expression)
    345:       as_sql_append(sql, ae.aliaz)
    346:     end

array_sql_append(sql, a)

SQL fragment for Array

[Source]

         # File lib/sequel/dataset/sql.rb, line 349
    349:     def array_sql_append(sql, a)
    350:       if a.empty?
    351:         sql << ARRAY_EMPTY
    352:       else
    353:         sql << PAREN_OPEN
    354:         expression_list_append(sql, a)
    355:         sql << PAREN_CLOSE
    356:       end
    357:     end

boolean_constant_sql_append(sql, constant)

SQL fragment for BooleanConstants

[Source]

         # File lib/sequel/dataset/sql.rb, line 360
    360:     def boolean_constant_sql_append(sql, constant)
    361:       if (constant == true || constant == false) && !supports_where_true?
    362:         sql << (constant == true ? CONDITION_TRUE : CONDITION_FALSE)
    363:       else
    364:         literal_append(sql, constant)
    365:       end
    366:     end

case_expression_sql_append(sql, ce)

SQL fragment for CaseExpression

[Source]

         # File lib/sequel/dataset/sql.rb, line 369
    369:     def case_expression_sql_append(sql, ce)
    370:       sql << CASE_OPEN
    371:       if ce.expression?
    372:         sql << SPACE
    373:         literal_append(sql, ce.expression)
    374:       end
    375:       w = CASE_WHEN
    376:       t = CASE_THEN
    377:       ce.conditions.each do |c,r|
    378:         sql << w
    379:         literal_append(sql, c)
    380:         sql << t
    381:         literal_append(sql, r)
    382:       end
    383:       sql << CASE_ELSE
    384:       literal_append(sql, ce.default)
    385:       sql << CASE_END
    386:     end

cast_sql_append(sql, expr, type)

SQL fragment for the SQL CAST expression

[Source]

         # File lib/sequel/dataset/sql.rb, line 389
    389:     def cast_sql_append(sql, expr, type)
    390:       sql << CAST_OPEN
    391:       literal_append(sql, expr)
    392:       sql << AS << db.cast_type_literal(type).to_s
    393:       sql << PAREN_CLOSE
    394:     end

column_all_sql_append(sql, ca)

SQL fragment for specifying all columns in a given table

[Source]

         # File lib/sequel/dataset/sql.rb, line 397
    397:     def column_all_sql_append(sql, ca)
    398:       quote_schema_table_append(sql, ca.table)
    399:       sql << COLUMN_ALL
    400:     end

complex_expression_sql_append(sql, op, args)

[Source]

         # File lib/sequel/dataset/sql.rb, line 402
    402:     def complex_expression_sql_append(sql, op, args)
    403:       case op
    404:       when *IS_OPERATORS
    405:         r = args.at(1)
    406:         if r.nil? || supports_is_true?
    407:           raise(InvalidOperation, 'Invalid argument used for IS operator') unless v = IS_LITERALS[r]
    408:           sql << PAREN_OPEN
    409:           literal_append(sql, args.at(0))
    410:           sql << SPACE << op.to_s << SPACE
    411:           sql << v << PAREN_CLOSE
    412:         elsif op == :IS
    413:           complex_expression_sql_append(sql, "=""=", args)
    414:         else
    415:           complex_expression_sql_append(sql, :OR, [SQL::BooleanExpression.new("!=""!=", *args), SQL::BooleanExpression.new(:IS, args.at(0), nil)])
    416:         end
    417:       when :IN, "NOT IN""NOT IN"
    418:         cols = args.at(0)
    419:         vals = args.at(1)
    420:         col_array = true if cols.is_a?(Array)
    421:         if vals.is_a?(Array)
    422:           val_array = true
    423:           empty_val_array = vals == []
    424:         end
    425:         if empty_val_array
    426:           literal_append(sql, empty_array_value(op, cols))
    427:         elsif col_array
    428:           if !supports_multiple_column_in?
    429:             if val_array
    430:               expr = SQL::BooleanExpression.new(:OR, *vals.to_a.map{|vs| SQL::BooleanExpression.from_value_pairs(cols.to_a.zip(vs).map{|c, v| [c, v]})})
    431:               literal_append(sql, op == :IN ? expr : ~expr)
    432:             else
    433:               old_vals = vals
    434:               vals = vals.naked if vals.is_a?(Sequel::Dataset)
    435:               vals = vals.to_a
    436:               val_cols = old_vals.columns
    437:               complex_expression_sql_append(sql, op, [cols, vals.map!{|x| x.values_at(*val_cols)}])
    438:             end
    439:           else
    440:             # If the columns and values are both arrays, use array_sql instead of
    441:             # literal so that if values is an array of two element arrays, it
    442:             # will be treated as a value list instead of a condition specifier.
    443:             sql << PAREN_OPEN
    444:             literal_append(sql, cols)
    445:             sql << SPACE << op.to_s << SPACE
    446:             if val_array
    447:               array_sql_append(sql, vals)
    448:             else
    449:               literal_append(sql, vals)
    450:             end
    451:             sql << PAREN_CLOSE
    452:           end
    453:         else
    454:           sql << PAREN_OPEN
    455:           literal_append(sql, cols)
    456:           sql << SPACE << op.to_s << SPACE
    457:           literal_append(sql, vals)
    458:           sql << PAREN_CLOSE
    459:         end
    460:       when *TWO_ARITY_OPERATORS
    461:         sql << PAREN_OPEN
    462:         literal_append(sql, args.at(0))
    463:         sql << SPACE << op.to_s << SPACE
    464:         literal_append(sql, args.at(1))
    465:         sql << PAREN_CLOSE
    466:       when *N_ARITY_OPERATORS
    467:         sql << PAREN_OPEN
    468:         c = false
    469:         op_str = " #{op} "
    470:         args.each do |a|
    471:           sql << op_str if c
    472:           literal_append(sql, a)
    473:           c ||= true
    474:         end
    475:         sql << PAREN_CLOSE
    476:       when :NOT
    477:         sql << NOT_SPACE
    478:         literal_append(sql, args.at(0))
    479:       when :NOOP
    480:         literal_append(sql, args.at(0))
    481:       when 'B~''B~'
    482:         sql << TILDE
    483:         literal_append(sql, args.at(0))
    484:       when :extract
    485:         sql << EXTRACT << args.at(0).to_s << FROM
    486:         literal_append(sql, args.at(1))
    487:         sql << PAREN_CLOSE
    488:       else
    489:         raise(InvalidOperation, "invalid operator #{op}")
    490:       end
    491:     end

constant_sql_append(sql, constant)

SQL fragment for constants

[Source]

         # File lib/sequel/dataset/sql.rb, line 494
    494:     def constant_sql_append(sql, constant)
    495:       sql << constant.to_s
    496:     end

function_sql_append(sql, f)

SQL fragment specifying an SQL function call

[Source]

         # File lib/sequel/dataset/sql.rb, line 499
    499:     def function_sql_append(sql, f)
    500:       sql << f.f.to_s
    501:       args = f.args
    502:       if args.empty?
    503:         sql << FUNCTION_EMPTY
    504:       else
    505:         literal_append(sql, args)
    506:       end
    507:     end

join_clause_sql_append(sql, jc)

SQL fragment specifying a JOIN clause without ON or USING.

[Source]

         # File lib/sequel/dataset/sql.rb, line 510
    510:     def join_clause_sql_append(sql, jc)
    511:       table = jc.table
    512:       table_alias = jc.table_alias
    513:       table_alias = nil if table == table_alias
    514:       sql << SPACE << join_type_sql(jc.join_type) << SPACE
    515:       table_ref_append(sql, table)
    516:       as_sql_append(sql, table_alias) if table_alias
    517:     end

join_on_clause_sql_append(sql, jc)

SQL fragment specifying a JOIN clause with ON.

[Source]

         # File lib/sequel/dataset/sql.rb, line 520
    520:     def join_on_clause_sql_append(sql, jc)
    521:       join_clause_sql_append(sql, jc)
    522:       sql << ON
    523:       literal_append(sql, filter_expr(jc.on))
    524:     end

join_using_clause_sql_append(sql, jc)

SQL fragment specifying a JOIN clause with USING.

[Source]

         # File lib/sequel/dataset/sql.rb, line 527
    527:     def join_using_clause_sql_append(sql, jc)
    528:       join_clause_sql_append(sql, jc)
    529:       sql << USING
    530:       column_list_append(sql, jc.using)
    531:       sql << PAREN_CLOSE
    532:     end

negative_boolean_constant_sql_append(sql, constant)

SQL fragment for NegativeBooleanConstants

[Source]

         # File lib/sequel/dataset/sql.rb, line 535
    535:     def negative_boolean_constant_sql_append(sql, constant)
    536:       sql << NOT_SPACE
    537:       boolean_constant_sql_append(sql, constant)
    538:     end

ordered_expression_sql_append(sql, oe)

SQL fragment for the ordered expression, used in the ORDER BY clause.

[Source]

         # File lib/sequel/dataset/sql.rb, line 542
    542:     def ordered_expression_sql_append(sql, oe)
    543:       literal_append(sql, oe.expression)
    544:       sql << (oe.descending ? DESC : ASC)
    545:       case oe.nulls
    546:       when :first
    547:         sql << NULLS_FIRST
    548:       when :last
    549:         sql << NULLS_LAST
    550:       end
    551:     end

placeholder_literal_string_sql_append(sql, pls)

SQL fragment for a literal string with placeholders

[Source]

         # File lib/sequel/dataset/sql.rb, line 554
    554:     def placeholder_literal_string_sql_append(sql, pls)
    555:       args = pls.args
    556:       sql << PAREN_OPEN if pls.parens
    557:       if args.is_a?(Hash)
    558:         re = /:(#{args.keys.map{|k| Regexp.escape(k.to_s)}.join('|')})\b/
    559:         if RUBY_VERSION >= '1.8.7'
    560:           str = pls.str
    561:           loop do
    562:             previous, q, str = str.partition(re)
    563:             sql << previous
    564:             literal_append(sql, args[($1||q[1..-1].to_s).to_sym]) unless q.empty?
    565:             break if str.empty?
    566:           end
    567:         else
    568:           sql << pls.str.gsub(re){literal(args[$1.to_sym])}
    569:         end
    570:       else
    571:         i = -1
    572:         if RUBY_VERSION >= '1.8.7'
    573:           str = pls.str
    574:           loop do
    575:             previous, q, str = str.partition(QUESTION_MARK)
    576:             sql << previous
    577:             literal_append(sql, args.at(i+=1)) unless q.empty?
    578:             break if str.empty?
    579:           end
    580:         else
    581:           sql << pls.str.gsub(QUESTION_MARK_RE){literal(args.at(i+=1))}
    582:         end
    583:       end
    584:       sql << PAREN_CLOSE if pls.parens
    585:     end

qualified_identifier_sql_append(sql, qcr)

SQL fragment for the qualifed identifier, specifying a table and a column (or schema and table).

[Source]

         # File lib/sequel/dataset/sql.rb, line 589
    589:     def qualified_identifier_sql_append(sql, qcr)
    590:       case t = qcr.table
    591:       when Symbol, SQL::QualifiedIdentifier, SQL::Identifier
    592:         literal_append(sql, t)
    593:       else
    594:         quote_identifier_append(sql, t)
    595:       end
    596:       sql << DOT
    597:       case c = qcr.column
    598:       when Symbol, SQL::QualifiedIdentifier, SQL::Identifier
    599:         literal_append(sql, c)
    600:       else
    601:         quote_identifier_append(sql, c)
    602:       end
    603:     end

quote_identifier_append(sql, name)

Adds quoting to identifiers (columns and tables). If identifiers are not being quoted, returns name as a string. If identifiers are being quoted quote the name with quoted_identifier.

[Source]

         # File lib/sequel/dataset/sql.rb, line 608
    608:     def quote_identifier_append(sql, name)
    609:       if name.is_a?(LiteralString)
    610:         sql << name
    611:       else
    612:         name = name.value if name.is_a?(SQL::Identifier)
    613:         name = input_identifier(name)
    614:         if quote_identifiers?
    615:           quoted_identifier_append(sql, name)
    616:         else
    617:           sql << name
    618:         end
    619:       end
    620:     end

quote_schema_table_append(sql, table)

Separates the schema from the table and returns a string with them quoted (if quoting identifiers)

[Source]

         # File lib/sequel/dataset/sql.rb, line 624
    624:     def quote_schema_table_append(sql, table)
    625:       schema, table = schema_and_table(table)
    626:       if schema
    627:         quote_identifier_append(sql, schema)
    628:         sql << DOT
    629:       end
    630:       quote_identifier_append(sql, table)
    631:     end

quoted_identifier_append(sql, name)

This method quotes the given name with the SQL standard double quote. should be overridden by subclasses to provide quoting not matching the SQL standard, such as backtick (used by MySQL and SQLite).

[Source]

         # File lib/sequel/dataset/sql.rb, line 636
    636:     def quoted_identifier_append(sql, name)
    637:       sql << QUOTE << name.to_s.gsub(QUOTE_RE, DOUBLE_QUOTE) << QUOTE
    638:     end

schema_and_table(table_name)

Split the schema information from the table

[Source]

         # File lib/sequel/dataset/sql.rb, line 641
    641:     def schema_and_table(table_name)
    642:       sch = db.default_schema if db
    643:       case table_name
    644:       when Symbol
    645:         s, t, a = split_symbol(table_name)
    646:         [s||sch, t]
    647:       when SQL::QualifiedIdentifier
    648:         [table_name.table, table_name.column]
    649:       when SQL::Identifier
    650:         [sch, table_name.value]
    651:       when String
    652:         [sch, table_name]
    653:       else
    654:         raise Error, 'table_name should be a Symbol, SQL::QualifiedIdentifier, SQL::Identifier, or String'
    655:       end
    656:     end

subscript_sql_append(sql, s)

SQL fragment for specifying subscripts (SQL array accesses)

[Source]

         # File lib/sequel/dataset/sql.rb, line 659
    659:     def subscript_sql_append(sql, s)
    660:       literal_append(sql, s.f)
    661:       sql << BRACKET_OPEN
    662:       expression_list_append(sql, s.sub)
    663:       sql << BRACKET_CLOSE
    664:     end

window_function_sql_append(sql, function, window)

The SQL fragment for the given window function‘s function and window.

[Source]

         # File lib/sequel/dataset/sql.rb, line 708
    708:     def window_function_sql_append(sql, function, window)
    709:       literal_append(sql, function)
    710:       sql << OVER
    711:       literal_append(sql, window)
    712:     end

window_sql_append(sql, opts)

The SQL fragment for the given window‘s options.

[Source]

         # File lib/sequel/dataset/sql.rb, line 667
    667:     def window_sql_append(sql, opts)
    668:       raise(Error, 'This dataset does not support window functions') unless supports_window_functions?
    669:       sql << PAREN_OPEN
    670:       window, part, order, frame = opts.values_at(:window, :partition, :order, :frame)
    671:       space = false
    672:       space_s = SPACE
    673:       if window
    674:         literal_append(sql, window)
    675:         space = true
    676:       end
    677:       if part
    678:         sql << space_s if space
    679:         sql << PARTITION_BY
    680:         expression_list_append(sql, Array(part))
    681:         space = true
    682:       end
    683:       if order
    684:         sql << space_s if space
    685:         sql << ORDER_BY_NS
    686:         expression_list_append(sql, Array(order))
    687:         space = true
    688:       end
    689:       case frame
    690:         when nil
    691:           # nothing
    692:         when :all
    693:           sql << space_s if space
    694:           sql << FRAME_ALL
    695:         when :rows
    696:           sql << space_s if space
    697:           sql << FRAME_ROWS
    698:         when String
    699:           sql << space_s if space
    700:           sql << frame
    701:         else
    702:           raise Error, "invalid window frame clause, should be :all, :rows, a string, or nil"
    703:       end
    704:       sql << PAREN_CLOSE
    705:     end

### Protected Instance methods

_insert_sql()

Formats in INSERT statement using the stored columns and values.

[Source]

         # File lib/sequel/dataset/sql.rb, line 717
    717:     def _insert_sql
    718:       clause_sql(:insert)
    719:     end

_update_sql()

Formats an UPDATE statement using the stored values.

[Source]

         # File lib/sequel/dataset/sql.rb, line 722
    722:     def _update_sql
    723:       clause_sql(:update)
    724:     end

compound_from_self()

Return a from_self dataset if an order or limit is specified, so it works as expected with UNION, EXCEPT, and INTERSECT clauses.

[Source]

         # File lib/sequel/dataset/sql.rb, line 728
    728:     def compound_from_self
    729:       (@opts[:limit] || @opts[:order]) ? from_self : self
    730:     end

## 7 - Mutation methods

These methods modify the receiving dataset and should be used with care.

### Classes and Modules

Module Sequel::Dataset::Pagination
Module Sequel::Dataset::QueryBlockCopy

### Constants

MUTATION_METHODS | = | QUERY_METHODS - [:paginate, :naked] |  | All methods that should have a ! method added that modifies the receiver.

### Attributes

identifier_input_method | [W] | Set the method to call on identifiers going into the database for this dataset
identifier_output_method | [W] | Set the method to call on identifiers coming the database for this dataset
quote_identifiers | [W] | Whether to quote identifiers for this dataset
row_proc | [RW] | The row_proc for this database, should be any object that responds to `call` with a single hash argument and returns the object you want each to return.

### Public Class methods

def_mutation_method(*meths)

Setup mutation (e.g. filter!) methods. These operate the same as the non-! methods, but replace the options of the current dataset with the options of the resulting dataset.

[Source]

        # File lib/sequel/dataset/mutation.rb, line 14
    14:     def self.def_mutation_method(*meths)
    15:       meths.each do |meth|
    16:         class_eval("def #{meth}!(*args, &block); mutation_method(:#{meth}, *args, &block) end", __FILE__, __LINE__)
    17:       end
    18:     end

introspect_all_columns()

Enable column introspection for every dataset.

[Source]

        # File lib/sequel/extensions/columns_introspection.rb, line 56
    56:     def self.introspect_all_columns
    57:       include ColumnsIntrospection
    58:       remove_method(:columns) if instance_methods(false).map{|x| x.to_s}.include?('columns')
    59:     end

### Public Instance methods

columns_without_introspection()

Alias for columns

def_mutation_method(*meths)

Add a mutation method to this dataset instance.

[Source]

        # File lib/sequel/dataset/mutation.rb, line 37
    37:     def def_mutation_method(*meths)
    38:       meths.each do |meth|
    39:         instance_eval("def #{meth}!(*args, &block); mutation_method(:#{meth}, *args, &block) end", __FILE__, __LINE__)
    40:       end
    41:     end

each_page(page_size) {|paginate(page_no, page_size, record_count)}| ...}

Yields a paginated dataset for each page and returns the receiver. Does a count to find the total number of records for this dataset.

[Source]

        # File lib/sequel/extensions/pagination.rb, line 20
    20:     def each_page(page_size)
    21:       raise(Error, "You cannot paginate a dataset that already has a limit") if @opts[:limit]
    22:       record_count = count
    23:       total_pages = (record_count / page_size.to_f).ceil
    24:       (1..total_pages).each{|page_no| yield paginate(page_no, page_size, record_count)}
    25:       self
    26:     end

naked!()

Remove the row_proc from the current dataset.

[Source]

        # File lib/sequel/dataset/mutation.rb, line 44
    44:     def naked!
    45:       self.row_proc = nil
    46:       self
    47:     end

paginate(page_no, page_size, record_count=nil)

Returns a paginated dataset. The returned dataset is limited to the page size at the correct offset, and extended with the Pagination module. If a record count is not provided, does a count of total number of records for this dataset.

[Source]

        # File lib/sequel/extensions/pagination.rb, line 11
    11:     def paginate(page_no, page_size, record_count=nil)
    12:       raise(Error, "You cannot paginate a dataset that already has a limit") if @opts[:limit]
    13:       paginated = limit(page_size, (page_no - 1) * page_size)
    14:       paginated.extend(Pagination)
    15:       paginated.set_pagination_info(page_no, page_size, record_count || count)
    16:     end

print(*cols)

Pretty prints the records in the dataset as plain-text table.

[Source]

        # File lib/sequel/extensions/pretty_table.rb, line 8
     8:     def print(*cols)
     9:       Sequel::PrettyTable.print(naked.all, cols.empty? ? columns : cols)
    10:     end

query(&block)

Translates a query block into a dataset. Query blocks can be useful when expressing complex SELECT statements, e.g.:

      dataset = DB[:items].query do
        select :x, :y, :z
        filter{|o| (o.x > 1) & (o.y > 2)}
        order :z.desc
      end

Which is the same as:

     dataset = DB[:items].select(:x, :y, :z).filter{|o| (o.x > 1) & (o.y > 2)}.order(:z.desc)

Note that inside a call to query, you cannot call each, insert, update, or delete (or any method that calls those), or Sequel will raise an error.

[Source]

        # File lib/sequel/extensions/query.rb, line 30
    30:     def query(&block)
    31:       copy = clone({})
    32:       copy.extend(QueryBlockCopy)
    33:       copy.instance_eval(&block)
    34:       clone(copy.opts)
    35:     end

to_dot()

Return a string that can be processed by the `dot` program (included with graphviz) in order to see a visualization of the dataset‘s abstract syntax tree.

[Source]

         # File lib/sequel/extensions/to_dot.rb, line 145
    145:     def to_dot
    146:       ToDot.output(self)
    147:     end

[Validate]