Class: Sequel::Dataset

Inherits:
Object show all
Includes:
Enumerable, SQL::AliasMethods, SQL::BooleanMethods, SQL::CastMethods, SQL::ComplexExpressionMethods, SQL::InequalityMethods, SQL::NumericMethods, SQL::OrderMethods, SQL::StringMethods
Defined in:
lib/sequel/dataset.rb,
lib/sequel/dataset/sql.rb,
lib/sequel/dataset/misc.rb,
lib/sequel/dataset/graph.rb,
lib/sequel/dataset/query.rb,
lib/sequel/dataset/actions.rb,
lib/sequel/dataset/mutation.rb,
lib/sequel/dataset/features.rb,
lib/sequel/extensions/query.rb,
lib/sequel/extensions/pagination.rb,
lib/sequel/adapters/utils/replace.rb,
lib/sequel/extensions/null_dataset.rb,
lib/sequel/extensions/split_array_nil.rb,
lib/sequel/dataset/prepared_statements.rb,
lib/sequel/adapters/utils/stored_procedures.rb

Overview

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.

Direct Known Subclasses

ADO::Dataset, Amalgalite::Dataset, Cubrid::Dataset, Sequel::DB2::Dataset, Sequel::DBI::Dataset, Sequel::DataObjects::Dataset, Firebird::Dataset, IBMDB::Dataset, Informix::Dataset, JDBC::Dataset, Mock::Dataset, MySQL::Dataset, Mysql2::Dataset, ODBC::Dataset, OpenBase::Dataset, Oracle::Dataset, Postgres::Dataset, SQLite::Dataset, SqlAnywhere::Dataset, Swift::Dataset, TinyTDS::Dataset

Defined Under Namespace

Modules: ArgumentMapper, NullDataset, Nullifiable, Pagination, PreparedStatementMethods, Replace, SplitArrayNil, StoredProcedureMethods, StoredProcedures, UnnumberedArgumentMapper Classes: Query

Constant Summary

OPTS =
Sequel::OPTS
EMULATED_FUNCTION_MAP =

Map of emulated function names to native function names.

{}
WILDCARD =
LiteralString.new('*').freeze
ALL =
' ALL'.freeze
AND_SEPARATOR =
" AND ".freeze
APOS =
"'".freeze
APOS_RE =
/'/.freeze
ARRAY_EMPTY =
'(NULL)'.freeze
AS =
' AS '.freeze
ASC =
' ASC'.freeze
BACKSLASH =
"\\".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
COLON =
':'.freeze
COLUMN_REF_RE1 =
Sequel::COLUMN_REF_RE1
COLUMN_REF_RE2 =
Sequel::COLUMN_REF_RE2
COLUMN_REF_RE3 =
Sequel::COLUMN_REF_RE3
COMMA =
', '.freeze
COMMA_SEPARATOR =
COMMA
CONDITION_FALSE =
'(1 = 0)'.freeze
CONDITION_TRUE =
'(1 = 1)'.freeze
COUNT_FROM_SELF_OPTS =
[:distinct, :group, :sql, :limit, :offset, :compounds]
COUNT_OF_ALL_AS_COUNT =
SQL::Function.new(:count, WILDCARD).as(:count)
DATASET_ALIAS_BASE_NAME =
't'.freeze
DEFAULT =
LiteralString.new('DEFAULT').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
ESCAPE =
" ESCAPE ".freeze
EXTRACT =
'extract('.freeze
EXISTS =
['EXISTS '.freeze].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
LATERAL =
'LATERAL '.freeze
LIKE_OPERATORS =
::Sequel::SQL::ComplexExpression::LIKE_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
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
SPACE_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
REGEXP_OPERATORS =
::Sequel::SQL::ComplexExpression::REGEXP_OPERATORS
UNDERSCORE =
'_'.freeze
UPDATE =
'UPDATE'.freeze
UPDATE_CLAUSE_METHODS =
clause_methods(:update, %w'update table set where')
USING =
' USING ('.freeze
VALUES =
" VALUES ".freeze
V190 =
'1.9.0'.freeze
WHERE =
" WHERE ".freeze
NOTIMPL_MSG =

:section: 6 - Miscellaneous methods These methods don't fit cleanly into another section.


"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
EXTENSIONS =

Hash of extension name symbols to callable objects to load the extension into the Dataset object (usually by extending it with a module defined in the extension).

{}
COLUMN_CHANGE_OPTS =

The dataset options that require the removal of cached columns if changed.

[:select, :sql, :from, :join].freeze
NON_SQL_OPTIONS =

Which options don't affect the SQL generation. Used by simple_select_all? to determine if this is a simple SELECT * FROM table.

[:server, :defaults, :overrides, :graph, :eager_graph, :graph_aliases]
CONDITIONED_JOIN_TYPES =

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.

[:inner, :full_outer, :right_outer, :left_outer, :full, :right, :left]
UNCONDITIONED_JOIN_TYPES =

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.

[:natural, :natural_left, :natural_right, :natural_full, :cross]
JOIN_METHODS =

All methods that return modified datasets with a joined table added.

(CONDITIONED_JOIN_TYPES + UNCONDITIONED_JOIN_TYPES).map{|x| "#{x}_join".to_sym} + [:join, :join_table]
QUERY_METHODS =

Methods that return modified datasets

(<<-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 offset or order order_append order_by order_more order_prepend qualify
  reverse reverse_order select select_all select_append select_group select_more server
  set_graph_aliases unfiltered ungraphed ungrouped union
  unlimited unordered where with with_recursive with_sql
METHS
ACTION_METHODS =

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

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

All methods that should have a ! method added that modifies the receiver.

QUERY_METHODS - [:naked, :from_self]
PREPARED_ARG_PLACEHOLDER =

:section: 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.


LiteralString.new('?').freeze

Instance Attribute Summary (collapse)

Class Method Summary (collapse)

Instance Method Summary (collapse)

Methods included from SQL::StringMethods

#ilike, #like

Methods included from SQL::OrderMethods

#asc, #desc

Methods included from SQL::NumericMethods

#+

Methods included from SQL::ComplexExpressionMethods

#extract, #sql_boolean, #sql_number, #sql_string

Methods included from SQL::CastMethods

#cast, #cast_numeric, #cast_string

Methods included from SQL::BooleanMethods

#~

Methods included from SQL::AliasMethods

#as

Constructor Details

- (Dataset) initialize(db)

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.



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# File 'lib/sequel/dataset/misc.rb', line 28

def initialize(db)
  @db = db
  @opts = OPTS
end

Instance Attribute Details

- (Object) db (readonly)

The database related to this dataset. This is the Database instance that will execute all of this dataset's queries.



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# File 'lib/sequel/dataset/misc.rb', line 15

def db
  @db
end

- (Object) opts (readonly)

The hash of options for this dataset, keys are symbols.



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# File 'lib/sequel/dataset/misc.rb', line 18

def opts
  @opts
end

- (Object) row_proc

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.



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# File 'lib/sequel/dataset/mutation.rb', line 31

def row_proc
  @row_proc
end

Class Method Details

+ (Object) 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.



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# File 'lib/sequel/dataset/sql.rb', line 177

def self.clause_methods(type, clauses)
  clauses.map{|clause| :#{type}_#{clause}_sql"}.freeze
end

+ (Object) 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.

Do not call this method with untrusted input, as that can result in arbitrary code execution.



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# File 'lib/sequel/dataset/mutation.rb', line 17

def self.def_mutation_method(*meths)
  options = meths.pop if meths.last.is_a?(Hash)
  mod = options[:module] if options
  mod ||= self
  meths.each do |meth|
    mod.class_eval("def #{meth}!(*args, &block); mutation_method(:#{meth}, *args, &block) end", __FILE__, __LINE__)
  end
end

+ (Object) register_extension(ext, mod = nil, &block)

Register an extension callback for Dataset objects. ext should be the extension name symbol, and mod should either be a Module that the dataset is extended with, or a callable object called with the database object. If mod is not provided, a block can be provided and is treated as the mod object.

If mod is a module, this also registers a Database extension that will extend all of the database's datasets.



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# File 'lib/sequel/dataset/query.rb', line 53

def self.register_extension(ext, mod=nil, &block)
  if mod
    raise(Error, "cannot provide both mod and block to Dataset.register_extension") if block
    if mod.is_a?(Module)
      block = proc{|ds| ds.extend(mod)}
      Sequel::Database.register_extension(ext){|db| db.extend_datasets(mod)}
    else
      block = mod
    end
  end
  Sequel.synchronize{EXTENSIONS[ext] = block}
end

Instance Method Details

- (Object) <<(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)


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# File 'lib/sequel/dataset/actions.rb', line 22

def <<(arg)
  insert(arg)
  self
end

- (Object) ==(o)

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



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# File 'lib/sequel/dataset/misc.rb', line 35

def ==(o)
  o.is_a?(self.class) && db == o.db && opts == o.opts && sql == o.sql
end

- (Object) [](*conditions)

Returns the first record matching the conditions. Examples:

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

Raises:



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# File 'lib/sequel/dataset/actions.rb', line 31

def [](*conditions)
  raise(Error, ARRAY_ACCESS_ERROR_MSG) if (conditions.length == 1 and conditions.first.is_a?(Integer)) or conditions.length == 0
  first(*conditions)
end

- (Object) 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


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# File 'lib/sequel/dataset/graph.rb', line 16

def add_graph_aliases(graph_aliases)
  unless (ga = opts[:graph_aliases]) || (opts[:graph] && (ga = opts[:graph][:column_aliases]))
    raise Error, "cannot call add_graph_aliases on a dataset that has not been called with graph or set_graph_aliases"
  end
  columns, graph_aliases = graph_alias_columns(graph_aliases)
  select_more(*columns).clone(:graph_aliases => ga.merge(graph_aliases))
end

- (Object) aliased_expression_sql_append(sql, ae)

SQL fragment for AliasedExpression



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# File 'lib/sequel/dataset/sql.rb', line 299

def aliased_expression_sql_append(sql, ae)
  literal_append(sql, ae.expression)
  as_sql_append(sql, ae.alias)
end

- (Object) 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}


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# File 'lib/sequel/dataset/actions.rb', line 44

def all(&block)
  a = []
  each{|r| a << r}
  post_load(a)
  a.each(&block) if block
  a
end

- (Object) and(*cond, &block)

Alias for where.



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# File 'lib/sequel/dataset/query.rb', line 67

def and(*cond, &block)
  where(*cond, &block)
end

- (Object) array_sql_append(sql, a)

SQL fragment for Array



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# File 'lib/sequel/dataset/sql.rb', line 305

def array_sql_append(sql, a)
  if a.empty?
    sql << ARRAY_EMPTY
  else
    sql << PAREN_OPEN
    expression_list_append(sql, a)
    sql << PAREN_CLOSE
  end
end

- (Object) avg(column = Sequel.virtual_row(&Proc.new))

Returns the average value for the given column/expression. Uses a virtual row block if no argument is given.

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


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# File 'lib/sequel/dataset/actions.rb', line 59

def avg(column=Sequel.virtual_row(&Proc.new))
  aggregate_dataset.get{avg(column).as(:avg)}
end

- (Object) 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}


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# File 'lib/sequel/dataset/prepared_statements.rb', line 217

def bind(bind_vars={})
  clone(:bind_vars=>@opts[:bind_vars] ? @opts[:bind_vars].merge(bind_vars) : bind_vars)
end

- (Object) boolean_constant_sql_append(sql, constant)

SQL fragment for BooleanConstants



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# File 'lib/sequel/dataset/sql.rb', line 316

def boolean_constant_sql_append(sql, constant)
  if (constant == true || constant == false) && !supports_where_true?
    sql << (constant == true ? CONDITION_TRUE : CONDITION_FALSE)
  else
    literal_append(sql, constant)
  end
end

- (Object) 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}


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# File 'lib/sequel/dataset/prepared_statements.rb', line 228

def call(type, bind_variables={}, *values, &block)
  prepare(type, nil, *values).call(bind_variables, &block)
end

- (Object) case_expression_sql_append(sql, ce)

SQL fragment for CaseExpression



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# File 'lib/sequel/dataset/sql.rb', line 325

def case_expression_sql_append(sql, ce)
  sql << CASE_OPEN
  if ce.expression?
    sql << SPACE
    literal_append(sql, ce.expression)
  end
  w = CASE_WHEN
  t = CASE_THEN
  ce.conditions.each do |c,r|
    sql << w
    literal_append(sql, c)
    sql << t
    literal_append(sql, r)
  end
  sql << CASE_ELSE
  literal_append(sql, ce.default)
  sql << CASE_END
end

- (Object) cast_sql_append(sql, expr, type)

SQL fragment for the SQL CAST expression



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# File 'lib/sequel/dataset/sql.rb', line 345

def cast_sql_append(sql, expr, type)
  sql << CAST_OPEN
  literal_append(sql, expr)
  sql << AS << db.cast_type_literal(type).to_s
  sql << PAREN_CLOSE
end

- (Object) clone(opts = nil)

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.



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# File 'lib/sequel/dataset/query.rb', line 75

def clone(opts = nil)
  c = super()
  if opts
    c.instance_variable_set(:@opts, @opts.merge(opts))
    c.instance_variable_set(:@columns, nil) if @columns && !opts.each_key{|o| break if COLUMN_CHANGE_OPTS.include?(o)}
  else
    c.instance_variable_set(:@opts, @opts.dup)
  end
  c
end

- (Object) column_all_sql_append(sql, ca)

SQL fragment for specifying all columns in a given table



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# File 'lib/sequel/dataset/sql.rb', line 353

def column_all_sql_append(sql, ca)
  qualified_identifier_sql_append(sql, ca.table, WILDCARD)
end

- (Object) 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]


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# File 'lib/sequel/dataset/actions.rb', line 72

def columns
  return @columns if @columns
  ds = unfiltered.unordered.naked.clone(:distinct => nil, :limit => 1, :offset=>nil)
  ds.each{break}
  @columns = ds.instance_variable_get(:@columns)
  @columns || []
end

- (Object) 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]


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# File 'lib/sequel/dataset/actions.rb', line 85

def columns!
  @columns = nil
  columns
end

- (Object) complex_expression_sql_append(sql, op, args)

SQL fragment for the complex expression.



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# File 'lib/sequel/dataset/sql.rb', line 358

def complex_expression_sql_append(sql, op, args)
  case op
  when *IS_OPERATORS
    r = args.at(1)
    if r.nil? || supports_is_true?
      raise(InvalidOperation, 'Invalid argument used for IS operator') unless val = IS_LITERALS[r]
      sql << PAREN_OPEN
      literal_append(sql, args.at(0))
      sql << SPACE << op.to_s << SPACE
      sql << val << PAREN_CLOSE
    elsif op == :IS
      complex_expression_sql_append(sql, :=", args)
    else
      complex_expression_sql_append(sql, :OR, [SQL::BooleanExpression.new(:!=", *args), SQL::BooleanExpression.new(:IS, args.at(0), nil)])
    end
  when :IN, :NOT IN"
    cols = args.at(0)
    vals = args.at(1)
    col_array = true if cols.is_a?(Array)
    if vals.is_a?(Array)
      val_array = true
      empty_val_array = vals == []
    end
    if empty_val_array
      literal_append(sql, empty_array_value(op, cols))
    elsif col_array
      if !supports_multiple_column_in?
        if val_array
          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]})})
          literal_append(sql, op == :IN ? expr : ~expr)
        else
          old_vals = vals
          vals = vals.naked if vals.is_a?(Sequel::Dataset)
          vals = vals.to_a
          val_cols = old_vals.columns
          complex_expression_sql_append(sql, op, [cols, vals.map!{|x| x.values_at(*val_cols)}])
        end
      else
        # If the columns and values are both arrays, use array_sql instead of
        # literal so that if values is an array of two element arrays, it
        # will be treated as a value list instead of a condition specifier.
        sql << PAREN_OPEN
        literal_append(sql, cols)
        sql << SPACE << op.to_s << SPACE
        if val_array
          array_sql_append(sql, vals)
        else
          literal_append(sql, vals)
        end
        sql << PAREN_CLOSE
      end
    else
      sql << PAREN_OPEN
      literal_append(sql, cols)
      sql << SPACE << op.to_s << SPACE
      literal_append(sql, vals)
      sql << PAREN_CLOSE
    end
  when :LIKE, :NOT LIKE'
    sql << PAREN_OPEN
    literal_append(sql, args.at(0))
    sql << SPACE << op.to_s << SPACE
    literal_append(sql, args.at(1))
    sql << ESCAPE
    literal_append(sql, BACKSLASH)
    sql << PAREN_CLOSE
  when :ILIKE, :NOT ILIKE'
    complex_expression_sql_append(sql, (op == :ILIKE ? :LIKE : :NOT LIKE"), args.map{|v| Sequel.function(:UPPER, v)})
  when *TWO_ARITY_OPERATORS
    if REGEXP_OPERATORS.include?(op) && !supports_regexp?
      raise InvalidOperation, "Pattern matching via regular expressions is not supported on #{db.database_type}"
    end
    sql << PAREN_OPEN
    literal_append(sql, args.at(0))
    sql << SPACE << op.to_s << SPACE
    literal_append(sql, args.at(1))
    sql << PAREN_CLOSE
  when *N_ARITY_OPERATORS
    sql << PAREN_OPEN
    c = false
    op_str = " #{op} "
    args.each do |a|
      sql << op_str if c
      literal_append(sql, a)
      c ||= true
    end
    sql << PAREN_CLOSE
  when :NOT
    sql << NOT_SPACE
    literal_append(sql, args.at(0))
  when :NOOP
    literal_append(sql, args.at(0))
  when :B~'
    sql << TILDE
    literal_append(sql, args.at(0))
  when :extract
    sql << EXTRACT << args.at(0).to_s << FROM
    literal_append(sql, args.at(1))
    sql << PAREN_CLOSE
  else
    raise(InvalidOperation, "invalid operator #{op}")
  end
end

- (Object) constant_sql_append(sql, constant)

SQL fragment for constants



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# File 'lib/sequel/dataset/sql.rb', line 463

def constant_sql_append(sql, constant)
  sql << constant.to_s
end

- (Object) count(arg = (no_arg=true), &block)

Returns the number of records in the dataset. If an argument is provided, it is used as the argument to count. If a block is provided, it is treated as a virtual row, and the result is used as the argument to count.

DB[:table].count # SELECT count(*) AS count FROM table LIMIT 1
# => 3
DB[:table].count(:column) # SELECT count(column) AS count FROM table LIMIT 1
# => 2
DB[:table].count{foo(column)} # SELECT count(foo(column)) AS count FROM table LIMIT 1
# => 1


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# File 'lib/sequel/dataset/actions.rb', line 101

def count(arg=(no_arg=true), &block)
  if no_arg
    if block
      arg = Sequel.virtual_row(&block)
      aggregate_dataset.get{count(arg).as(:count)}
    else
      aggregate_dataset.get{count{}.*.as(:count)}.to_i
    end
  elsif block
    raise Error, 'cannot provide both argument and block to Dataset#count'
  else
    aggregate_dataset.get{count(arg).as(:count)}
  end
end

- (Object) delayed_evaluation_sql_append(sql, callable)

SQL fragment for delayed evaluations, evaluating the object and literalizing the returned value.



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# File 'lib/sequel/dataset/sql.rb', line 469

def delayed_evaluation_sql_append(sql, callable)
  literal_append(sql, callable.call)
end

- (Object) 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


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# File 'lib/sequel/dataset/actions.rb', line 121

def delete(&block)
  sql = delete_sql
  if uses_returning?(:delete)
    returning_fetch_rows(sql, &block)
  else
    execute_dui(sql)
  end
end

- (Object) delete_sql

Returns a DELETE SQL query string. See delete.

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


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# File 'lib/sequel/dataset/sql.rb', line 12

def delete_sql
  return static_sql(opts[:sql]) if opts[:sql]
  check_modification_allowed!
  clause_sql(:delete)
end

- (Object) 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

Raises:



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# File 'lib/sequel/dataset/query.rb', line 95

def distinct(*args)
  raise(InvalidOperation, "DISTINCT ON not supported") if !args.empty? && !supports_distinct_on?
  clone(:distinct => args)
end

- (Object) dup

Similar to #clone, but returns an unfrozen clone if the receiver is frozen.



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# File 'lib/sequel/dataset/misc.rb', line 45

def dup
  o = clone
  o.opts.delete(:frozen)
  o
end

- (Object) each

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.



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# File 'lib/sequel/dataset/actions.rb', line 139

def each
  if row_proc = @row_proc
    fetch_rows(select_sql){|r| yield row_proc.call(r)}
  else
    fetch_rows(select_sql){|r| yield r}
  end
  self
end

- (Object) each_server

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')}


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# File 'lib/sequel/dataset/misc.rb', line 56

def each_server
  db.servers.each{|s| yield server(s)}
end

- (Boolean) empty?

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

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

Returns:

  • (Boolean)


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# File 'lib/sequel/dataset/actions.rb', line 152

def empty?
  get(Sequel::SQL::AliasedExpression.new(1, :one)).nil?
end

- (Object) emulated_function_sql_append(sql, f)

SQL fragment specifying an emulated SQL function call. By default, assumes just the function name may need to be emulated, adapters should set an EMULATED_FUNCTION_MAP hash mapping emulated functions to native functions in their dataset class to setup the emulation.



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# File 'lib/sequel/dataset/sql.rb', line 478

def emulated_function_sql_append(sql, f)
  _function_sql_append(sql, native_function_name(f.f), f.args)
end

- (Boolean) eql?(o)

Alias for ==

Returns:

  • (Boolean)


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# File 'lib/sequel/dataset/misc.rb', line 40

def eql?(o)
  self == o
end

- (Object) escape_like(string)

Returns the string with the LIKE metacharacters (% and _) escaped. Useful for when the LIKE term is a user-provided string where metacharacters should not be recognized. Example:

ds.escape_like("foo\\%_") # 'foo\\\%\_'


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# File 'lib/sequel/dataset/misc.rb', line 65

def escape_like(string)
  string.gsub(/[\\%_]/){|m| "\\#{m}"}
end

- (Object) except(dataset, opts = 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

Raises:



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# File 'lib/sequel/dataset/query.rb', line 117

def except(dataset, opts=OPTS)
  raise(InvalidOperation, "EXCEPT not supported") unless supports_intersect_except?
  raise(InvalidOperation, "EXCEPT ALL not supported") if opts[:all] && !supports_intersect_except_all?
  compound_clone(:except, dataset, opts)
end

- (Object) exclude(*cond, &block)

Performs the inverse of Dataset#where. 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))


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# File 'lib/sequel/dataset/query.rb', line 131

def exclude(*cond, &block)
  _filter_or_exclude(true, :where, *cond, &block)
end

- (Object) 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)


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# File 'lib/sequel/dataset/query.rb', line 139

def exclude_having(*cond, &block)
  _filter_or_exclude(true, :having, *cond, &block)
end

- (Object) exclude_where(*cond, &block)

Alias for exclude.



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# File 'lib/sequel/dataset/query.rb', line 144

def exclude_where(*cond, &block)
  exclude(*cond, &block)
end

- (Object) 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))


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# File 'lib/sequel/dataset/sql.rb', line 22

def exists
  SQL::PlaceholderLiteralString.new(EXISTS, [self], true)
end

- (Object) extension(*exts)

Return a clone of the dataset loaded with the extensions, see #extension!.



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# File 'lib/sequel/dataset/query.rb', line 149

def extension(*exts)
  clone.extension!(*exts)
end

- (Object) extension!(*exts)

Load an extension into the receiver. In addition to requiring the extension file, this also modifies the dataset to work with the extension (usually extending it with a module defined in the extension file). If no related extension file exists or the extension does not have specific support for Database objects, an Error will be raised. Returns self.



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# File 'lib/sequel/dataset/mutation.rb', line 38

def extension!(*exts)
  raise_if_frozen!
  Sequel.extension(*exts)
  exts.each do |ext|
    if pr = Sequel.synchronize{EXTENSIONS[ext]}
      pr.call(self)
    else
      raise(Error, "Extension #{ext} does not have specific support handling individual datasets")
    end
  end
  self
end

- (Object) filter(*cond, &block)

Alias for where.



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# File 'lib/sequel/dataset/query.rb', line 154

def filter(*cond, &block)
  where(*cond, &block)
end

- (Object) 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.

If there are no records in the dataset, returns nil (or an empty array if an integer argument is given).

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}]


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# File 'lib/sequel/dataset/actions.rb', line 191

def first(*args, &block)
  ds = block ? filter(&block) : self

  if args.empty?
    ds.single_record
  else
    args = (args.size == 1) ? args.first : args
    if args.is_a?(Integer)
      ds.limit(args).all
    else
      ds.filter(args).single_record
    end
  end
end

- (Object) first!(*args, &block)

Calls first. If first returns nil (signaling that no row matches), raise a Sequel::NoMatchingRow exception.



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# File 'lib/sequel/dataset/actions.rb', line 208

def first!(*args, &block)
  first(*args, &block) || raise(Sequel::NoMatchingRow)
end

- (Object) first_source

Alias of first_source_alias



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# File 'lib/sequel/dataset/misc.rb', line 81

def first_source
  first_source_alias
end

- (Object) 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


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# File 'lib/sequel/dataset/misc.rb', line 93

def first_source_alias
  source = @opts[:from]
  if source.nil? || source.empty?
    raise Error, 'No source specified for query'
  end
  case s = source.first
  when SQL::AliasedExpression
    s.alias
  when Symbol
    _, _, aliaz = split_symbol(s)
    aliaz ? aliaz.to_sym : s
  else
    s
  end
end

- (Object) 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


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# File 'lib/sequel/dataset/misc.rb', line 118

def first_source_table
  source = @opts[:from]
  if source.nil? || source.empty?
    raise Error, 'No source specified for query'
  end
  case s = source.first
  when SQL::AliasedExpression
    s.expression
  when Symbol
    sch, table, aliaz = split_symbol(s)
    aliaz ? (sch ? SQL::QualifiedIdentifier.new(sch, table) : table.to_sym) : s
  else
    s
  end
end

- (Object) for_update

Returns a cloned dataset with a :update lock style.

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


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# File 'lib/sequel/dataset/query.rb', line 161

def for_update
  lock_style(:update)
end

- (Object) freeze

Sets the frozen flag on the dataset, so you can't modify it. Returns the receiver.



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# File 'lib/sequel/dataset/misc.rb', line 70

def freeze
  @opts[:frozen] = true
  self
end

- (Object) from(*source, &block)

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. If a block is given, it is treated as a virtual row block, similar to where.

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


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# File 'lib/sequel/dataset/query.rb', line 174

def from(*source, &block)
  virtual_row_columns(source, block)
  table_alias_num = 0
  ctes = nil
  source.map! do |s|
    case s
    when Dataset
      if hoist_cte?(s)
        ctes ||= []
        ctes += s.opts[:with]
        s = s.clone(:with=>nil)
      end
      SQL::AliasedExpression.new(s, dataset_alias(table_alias_num+=1))
    when Symbol
      sch, table, aliaz = split_symbol(s)
      if aliaz
        s = sch ? SQL::QualifiedIdentifier.new(sch, table) : SQL::Identifier.new(table)
        SQL::AliasedExpression.new(s, aliaz.to_sym)
      else
        s
      end
    else
      s
    end
  end
  o = {:from=>source.empty? ? nil : source}
  o[:with] = (opts[:with] || []) + ctes if ctes
  o[:num_dataset_sources] = table_alias_num if table_alias_num > 0
  clone(o)
end

- (Object) from_self(opts = 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


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# File 'lib/sequel/dataset/query.rb', line 216

def from_self(opts=OPTS)
  fs = {}
  @opts.keys.each{|k| fs[k] = nil unless NON_SQL_OPTIONS.include?(k)}
  clone(fs).from(opts[:alias] ? as(opts[:alias]) : self)
end

- (Object) from_self!(*args, &block)

Avoid self-referential dataset by cloning.



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# File 'lib/sequel/dataset/mutation.rb', line 52

def from_self!(*args, &block)
  raise_if_frozen!
  @opts = clone.from_self(*args, &block).opts
  self
end

- (Boolean) frozen?

Whether the object is frozen.

Returns:

  • (Boolean)


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# File 'lib/sequel/dataset/misc.rb', line 76

def frozen?
  @opts[:frozen]
end

- (Object) function_sql_append(sql, f)

SQL fragment specifying an SQL function call without emulation.



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# File 'lib/sequel/dataset/sql.rb', line 483

def function_sql_append(sql, f)
  _function_sql_append(sql, f.f, f.args)
end

- (Object) get(column = (no_arg=true; 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) AS v FROM table LIMIT 1
# => 6

You can pass an array of arguments to return multiple arguments, but you must make sure each element in the array has an alias that Sequel can determine:

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

DB[:table].get{[sum(id).as(sum), name]} # SELECT sum(id) AS sum, name FROM table LIMIT 1
# => [6, 'foo']


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# File 'lib/sequel/dataset/actions.rb', line 230

def get(column=(no_arg=true; nil), &block)
  ds = naked
  if block
    raise(Error, ARG_BLOCK_ERROR_MSG) unless no_arg
    ds = ds.select(&block)
    column = ds.opts[:select]
    column = nil if column.is_a?(Array) && column.length < 2
  else
    ds = if column.is_a?(Array)
      ds.select(*column)
    else
      ds.select(auto_alias_expression(column))
    end
  end

  if column.is_a?(Array)
   if r = ds.single_record
     r.values_at(*hash_key_symbols(column))
   end
  else
    ds.single_value
  end
end

- (Object) graph(dataset, join_conditions = nil, options = OPTS, &block)

Similar to Dataset#join_table, but uses unambiguous aliases for selected columns and keeps metadata about the aliases for use in other methods.

Arguments:

dataset

Can be a symbol (specifying a table), another dataset, or an SQL::Identifier, SQL::QualifiedIdentifier, or SQL::AliasedExpression.

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.

:qualify

The type of qualification to do, see #join_table.

: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 alias (or table) name is used more than once.



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# File 'lib/sequel/dataset/graph.rb', line 49

def graph(dataset, join_conditions = nil, options = OPTS, &block)
  # Allow the use of a dataset or symbol as the first argument
  # Find the table name/dataset based on the argument
  table_alias = options[:table_alias]
  table = dataset
  create_dataset = true

  case dataset
  when Symbol
    # let alias be the same as the table name (sans any optional schema)
    # unless alias explicitly given in the symbol using ___ notation
    table_alias ||= split_symbol(table).compact.last
  when Dataset
    if dataset.simple_select_all?
      table = dataset.opts[:from].first
      table_alias ||= table
    else
      table_alias ||= dataset_alias((@opts[:num_dataset_sources] || 0)+1)
    end
    create_dataset = false
  when SQL::Identifier
    table_alias ||= table.value
  when SQL::QualifiedIdentifier
    table_alias ||= split_qualifiers(table).last
  when SQL::AliasedExpression
    return graph(table.expression, join_conditions, {:table_alias=>table.alias}.merge(options), &block)
  else
    raise Error, "The dataset argument should be a symbol or dataset"
  end
  table_alias = table_alias.to_sym

  if create_dataset
    dataset = db.from(table)
  end

  # Raise Sequel::Error with explanation that the table alias has been used
  raise_alias_error = lambda do
    raise(Error, "this #{options[:table_alias] ? 'alias' : 'table'} has already been been used, please specify " \
      "#{options[:table_alias] ? 'a different alias' : 'an alias via the :table_alias option'}") 
  end

  # Only allow table aliases that haven't been used
  raise_alias_error.call if @opts[:graph] && @opts[:graph][:table_aliases] && @opts[:graph][:table_aliases].include?(table_alias)
  
  table_alias_qualifier = qualifier_from_alias_symbol(table_alias, table)
  implicit_qualifier = options[:implicit_qualifier]
  ds = self

  # Use a from_self if this is already a joined table (or from_self specifically disabled for graphs)
  if (@opts[:graph_from_self] != false && !@opts[:graph] && (@opts[:from].length > 1 || @opts[:join]))
    implicit_qualifier = options[:from_self_alias] || first_source
    ds = ds.from_self(:alias=>implicit_qualifier)
  end
  
  # Join the table early in order to avoid cloning the dataset twice
  ds = ds.join_table(options[:join_type] || :left_outer, table, join_conditions, :table_alias=>table_alias_qualifier, :implicit_qualifier=>implicit_qualifier, :qualify=>options[:qualify], &block)
  opts = ds.opts

  # Whether to include the table in the result set
  add_table = options[:select] == false ? false : true
  # Whether to add the columns to the list of column aliases
  add_columns = !ds.opts.include?(:graph_aliases)

  # Setup the initial graph data structure if it doesn't exist
  if graph = opts[:graph]
    opts[:graph] = graph = graph.dup
    select = opts[:select].dup
    [:column_aliases, :table_aliases, :column_alias_num].each{|k| graph[k] = graph[k].dup}
  else
    qualifier = ds.first_source_alias
    master = alias_symbol(qualifier)
    raise_alias_error.call if master == table_alias
    # Master hash storing all .graph related information
    graph = opts[:graph] = {}
    # Associates column aliases back to tables and columns
    column_aliases = graph[:column_aliases] = {}
    # Associates table alias (the master is never aliased)
    table_aliases = graph[:table_aliases] = {master=>self}
    # Keep track of the alias numbers used
    ca_num = graph[:column_alias_num] = Hash.new(0)
    # All columns in the master table are never
    # aliased, but are not included if set_graph_aliases
    # has been used.
    if add_columns
      if (select = @opts[:select]) && !select.empty? && !(select.length == 1 && (select.first.is_a?(SQL::ColumnAll)))
        select = select.each do |sel|
          column = case sel
          when Symbol
            _, c, a = split_symbol(sel)
            (a || c).to_sym
          when SQL::Identifier
            sel.value.to_sym
          when SQL::QualifiedIdentifier
            column = sel.column
            column = column.value if column.is_a?(SQL::Identifier)
            column.to_sym
          when SQL::AliasedExpression
            column = sel.alias
            column = column.value if column.is_a?(SQL::Identifier)
            column.to_sym
          else
            raise Error, "can't figure out alias to use for graphing for #{sel.inspect}"
          end
          column_aliases[column] = [master, column]
        end
        select = qualified_expression(select, qualifier)
      else
        select = columns.map do |column|
          column_aliases[column] = [master, column]
          SQL::QualifiedIdentifier.new(qualifier, column)
        end
      end
    end
  end

  # Add the table alias to the list of aliases
  # Even if it isn't been used in the result set,
  # we add a key for it with a nil value so we can check if it
  # is used more than once
  table_aliases = graph[:table_aliases]
  table_aliases[table_alias] = add_table ? dataset : nil

  # Add the columns to the selection unless we are ignoring them
  if add_table && add_columns
    column_aliases = graph[:column_aliases]
    ca_num = graph[:column_alias_num]
    # Which columns to add to the result set
    cols = options[:select] || dataset.columns
    # If the column hasn't been used yet, don't alias it.
    # If it has been used, try table_column.
    # If that has been used, try table_column_N 
    # using the next value of N that we know hasn't been
    # used
    cols.each do |column|
      col_alias, identifier = if column_aliases[column]
        column_alias = :#{table_alias}_#{column}"
        if column_aliases[column_alias]
          column_alias_num = ca_num[column_alias]
          column_alias = :#{column_alias}_#{column_alias_num}" 
          ca_num[column_alias] += 1
        end
        [column_alias, SQL::AliasedExpression.new(SQL::QualifiedIdentifier.new(table_alias_qualifier, column), column_alias)]
      else
        ident = SQL::QualifiedIdentifier.new(table_alias_qualifier, column)
        [column, ident]
      end
      column_aliases[col_alias] = [table_alias, column]
      select.push(identifier)
    end
  end
  add_columns ? ds.select(*select) : ds
end

- (Object) grep(columns, patterns, opts = 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%'))


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# File 'lib/sequel/dataset/query.rb', line 253

def grep(columns, patterns, opts=OPTS)
  if opts[:all_patterns]
    conds = Array(patterns).map do |pat|
      SQL::BooleanExpression.new(opts[:all_columns] ? :AND : :OR, *Array(columns).map{|c| SQL::StringExpression.like(c, pat, opts)})
    end
    where(SQL::BooleanExpression.new(opts[:all_patterns] ? :AND : :OR, *conds))
  else
    conds = Array(columns).map do |c|
      SQL::BooleanExpression.new(:OR, *Array(patterns).map{|pat| SQL::StringExpression.like(c, pat, opts)})
    end
    where(SQL::BooleanExpression.new(opts[:all_columns] ? :AND : :OR, *conds))
  end
end

- (Object) 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 where.

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)


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# File 'lib/sequel/dataset/query.rb', line 274

def group(*columns, &block)
  virtual_row_columns(columns, block)
  clone(:group => (columns.compact.empty? ? nil : columns))
end

- (Object) 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 where.

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}, ...]


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# File 'lib/sequel/dataset/query.rb', line 305

def group_and_count(*columns, &block)
  select_group(*columns, &block).select_more(COUNT_OF_ALL_AS_COUNT)
end

- (Object) group_by(*columns, &block)

Alias of group



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# File 'lib/sequel/dataset/query.rb', line 280

def group_by(*columns, &block)
  group(*columns, &block)
end

- (Object) group_cube

Adds the appropriate CUBE syntax to GROUP BY.

Raises:



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# File 'lib/sequel/dataset/query.rb', line 310

def group_cube
  raise Error, "GROUP BY CUBE not supported on #{db.database_type}" unless supports_group_cube?
  clone(:group_options=>:cube)
end

- (Object) group_rollup

Adds the appropriate ROLLUP syntax to GROUP BY.

Raises:



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# File 'lib/sequel/dataset/query.rb', line 316

def group_rollup
  raise Error, "GROUP BY ROLLUP not supported on #{db.database_type}" unless supports_group_rollup?
  clone(:group_options=>:rollup)
end

- (Object) hash

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



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# File 'lib/sequel/dataset/misc.rb', line 136

def hash
  [db, opts, sql].hash
end

- (Object) having(*cond, &block)

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

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


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# File 'lib/sequel/dataset/query.rb', line 325

def having(*cond, &block)
  _filter(:having, *cond, &block)
end

- (Object) identifier_input_method

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



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# File 'lib/sequel/dataset/misc.rb', line 142

def identifier_input_method
  if defined?(@identifier_input_method)
    @identifier_input_method
  else
    @identifier_input_method = db.identifier_input_method
  end
end

- (Object) identifier_input_method=(v)

Set the method to call on identifiers going into the database for this dataset



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# File 'lib/sequel/dataset/mutation.rb', line 59

def identifier_input_method=(v)
  raise_if_frozen!
  @identifier_input_method = v
end

- (Object) identifier_output_method

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



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# File 'lib/sequel/dataset/misc.rb', line 152

def identifier_output_method
  if defined?(@identifier_output_method)
    @identifier_output_method
  else
    @identifier_output_method = db.identifier_output_method
  end
end

- (Object) identifier_output_method=(v)

Set the method to call on identifiers coming the database for this dataset



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# File 'lib/sequel/dataset/mutation.rb', line 65

def identifier_output_method=(v)
  raise_if_frozen!
  @identifier_output_method = v
end

- (Object) import(columns, values, opts = 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.

:return

When the :value is :primary_key, returns an array of autoincremented primary key values for the rows inserted.

:server

Set the server/shard to use for the transaction and insert queries.

:slice

Same as :commit_every, :commit_every takes precedence.

Raises:



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# File 'lib/sequel/dataset/actions.rb', line 279

def import(columns, values, opts=OPTS)
  return @db.transaction{insert(columns, values)} if values.is_a?(Dataset)

  return if values.empty?
  raise(Error, IMPORT_ERROR_MSG) if columns.empty?
  ds = opts[:server] ? server(opts[:server]) : self
  
  if slice_size = opts[:commit_every] || opts[:slice]
    offset = 0
    rows = []
    while offset < values.length
      rows << ds._import(columns, values[offset, slice_size], opts)
      offset += slice_size
    end
    rows.flatten
  else
    ds._import(columns, values, opts)
  end
end

- (Object) 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


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# File 'lib/sequel/dataset/actions.rb', line 334

def insert(*values, &block)
  sql = insert_sql(*values)
  if uses_returning?(:insert)
    returning_fetch_rows(sql, &block)
  else
    execute_insert(sql)
  end
end

- (Object) insert_sql(*values)

Returns an INSERT SQL query string. See insert.

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


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# File 'lib/sequel/dataset/sql.rb', line 30

def insert_sql(*values)
  return static_sql(@opts[:sql]) if @opts[:sql]

  check_modification_allowed!

  columns = []

  case values.size
  when 0
    return insert_sql({})
  when 1
    case vals = values.at(0)
    when Hash
      values = []
      vals.each do |k,v| 
        columns << k
        values << v
      end
    when Dataset, Array, LiteralString
      values = vals
    end
  when 2
    if (v0 = values.at(0)).is_a?(Array) && ((v1 = values.at(1)).is_a?(Array) || v1.is_a?(Dataset) || v1.is_a?(LiteralString))
      columns, values = v0, v1
      raise(Error, "Different number of values and columns given to insert_sql") if values.is_a?(Array) and columns.length != values.length
    end
  end

  if values.is_a?(Array) && values.empty? && !insert_supports_empty_values? 
    columns = [columns().last]
    values = [DEFAULT]
  end
  clone(:columns=>columns, :values=>values)._insert_sql
end

- (Object) inspect

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



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# File 'lib/sequel/dataset/misc.rb', line 162

def inspect
  "#<#{visible_class_name}: #{sql.inspect}>"
end

- (Object) intersect(dataset, opts = 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

Raises:



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# File 'lib/sequel/dataset/query.rb', line 346

def intersect(dataset, opts=OPTS)
  raise(InvalidOperation, "INTERSECT not supported") unless supports_intersect_except?
  raise(InvalidOperation, "INTERSECT ALL not supported") if opts[:all] && !supports_intersect_except_all?
  compound_clone(:intersect, dataset, opts)
end

- (Object) interval(column = Sequel.virtual_row(&Proc.new))

Returns the interval between minimum and maximum values for the given column/expression. Uses a virtual row block if no argument is given.

DB[:table].interval(:id) # SELECT (max(id) - min(id)) FROM table LIMIT 1
# => 6
DB[:table].interval{function(column)} # SELECT (max(function(column)) - min(function(column))) FROM table LIMIT 1
# => 7


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# File 'lib/sequel/dataset/actions.rb', line 350

def interval(column=Sequel.virtual_row(&Proc.new))
  aggregate_dataset.get{(max(column) - min(column)).as(:interval)}
end

- (Object) invert

Inverts the current WHERE and HAVING clauses. If there is neither a WHERE or HAVING clause, adds a WHERE clause that is always false.

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

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


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# File 'lib/sequel/dataset/query.rb', line 360

def invert
  having, where = @opts.values_at(:having, :where)
  if having.nil? && where.nil?
    where(false)
  else
    o = {}
    o[:having] = SQL::BooleanExpression.invert(having) if having
    o[:where] = SQL::BooleanExpression.invert(where) if where
    clone(o)
  end
end

- (Object) join(*args, &block)

Alias of inner_join



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# File 'lib/sequel/dataset/query.rb', line 373

def join(*args, &block)
  inner_join(*args, &block)
end

- (Object) join_clause_sql_append(sql, jc)

SQL fragment specifying a JOIN clause without ON or USING.



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# File 'lib/sequel/dataset/sql.rb', line 488

def join_clause_sql_append(sql, jc)
  table = jc.table
  table_alias = jc.table_alias
  table_alias = nil if table == table_alias
  sql << SPACE << join_type_sql(jc.join_type) << SPACE
  identifier_append(sql, table)
  as_sql_append(sql, table_alias) if table_alias
end

- (Object) join_on_clause_sql_append(sql, jc)

SQL fragment specifying a JOIN clause with ON.



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# File 'lib/sequel/dataset/sql.rb', line 498

def join_on_clause_sql_append(sql, jc)
  join_clause_sql_append(sql, jc)
  sql << ON
  literal_append(sql, filter_expr(jc.on))
end

- (Object) join_table(type, table, expr = nil, options = OPTS, &block)

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

    • 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 where, 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.

    • :qualify - Can be set to false to not do any implicit qualification. Can be set to :deep to use the Qualifier AST Transformer, which will attempt to qualify subexpressions of the expression tree. Can be set to :symbol to only qualify symbols. Defaults to the value of default_join_table_qualification.

  • 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 where, 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|
  (Sequel.qualify(ta, :d) > Sequel.qualify(jta, :e)) & {Sequel.qualify(ta, :f)=>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)))


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# File 'lib/sequel/dataset/query.rb', line 431

def join_table(type, table, expr=nil, options=OPTS, &block)
  if hoist_cte?(table)
    s, ds = hoist_cte(table)
    return s.join_table(type, ds, expr, options, &block)
  end

  using_join = expr.is_a?(Array) && !expr.empty? && expr.all?{|x| x.is_a?(Symbol)}
  if using_join && !supports_join_using?
    h = {}
    expr.each{|e| h[e] = e}
    return join_table(type, table, h, options)
  end

  table_alias = options[:table_alias]
  last_alias = options[:implicit_qualifier]
  qualify_type = options[:qualify]

  if table.is_a?(Dataset)
    if table_alias.nil?
      table_alias_num = (@opts[:num_dataset_sources] || 0) + 1
      table_alias = dataset_alias(table_alias_num)
    end
    table_name = table_alias
  else
    table, implicit_table_alias = split_alias(table)
    table_alias ||= implicit_table_alias
    table_name = table_alias || table
  end

  join = if expr.nil? and !block
    SQL::JoinClause.new(type, table, table_alias)
  elsif using_join
    raise(Sequel::Error, "can't use a block if providing an array of symbols as expr") if block
    SQL::JoinUsingClause.new(expr, type, table, table_alias)
  else
    last_alias ||= @opts[:last_joined_table] || first_source_alias
    if Sequel.condition_specifier?(expr)
      expr = expr.collect do |k, v|
        qualify_type = default_join_table_qualification if qualify_type.nil?
        case qualify_type
        when false
          nil # Do no qualification
        when :deep
          k = Sequel::Qualifier.new(self, table_name).transform(k)
          v = Sequel::Qualifier.new(self, last_alias).transform(v)
        else
          k = qualified_column_name(k, table_name) if k.is_a?(Symbol)
          v = qualified_column_name(v, last_alias) if v.is_a?(Symbol)
        end
        [k,v]
      end
      expr = SQL::BooleanExpression.from_value_pairs(expr)
    end
    if block
      expr2 = yield(table_name, last_alias, @opts[:join] || [])
      expr = expr ? SQL::BooleanExpression.new(:AND, expr, expr2) : expr2
    end
    SQL::JoinOnClause.new(expr, type, table, table_alias)
  end

  opts = {:join => (@opts[:join] || []) + [join], :last_joined_table => table_name}
  opts[:num_dataset_sources] = table_alias_num if table_alias_num
  clone(opts)
end

- (Object) join_using_clause_sql_append(sql, jc)

SQL fragment specifying a JOIN clause with USING.



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# File 'lib/sequel/dataset/sql.rb', line 505

def join_using_clause_sql_append(sql, jc)
  join_clause_sql_append(sql, jc)
  sql << USING
  column_list_append(sql, jc.using)
  sql << PAREN_CLOSE
end

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

Raises:



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# File 'lib/sequel/dataset/actions.rb', line 364

def last(*args, &block)
  raise(Error, 'No order specified') unless @opts[:order]
  reverse.first(*args, &block)
end

- (Object) lateral

Marks this dataset as a lateral dataset. If used in another dataset's FROM or JOIN clauses, it will surround the subquery with LATERAL to enable it to deal with previous tables in the query:

DB.from(:a, DB[:b].where(:a__c=>:b__d).lateral)
# SELECT * FROM a, LATERAL (SELECT * FROM b WHERE (a.c = b.d))


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# File 'lib/sequel/dataset/query.rb', line 509

def lateral
  clone(:lateral=>true)
end

- (Object) limit(l, o = (no_offset = true; 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


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# File 'lib/sequel/dataset/query.rb', line 523

def limit(l, o = (no_offset = true; nil))
  return from_self.limit(l, o) if @opts[:sql]

  if l.is_a?(Range)
    no_offset = false
    o = l.first
    l = l.last - l.first + (l.exclude_end? ? 0 : 1)
  end
  l = l.to_i if l.is_a?(String) && !l.is_a?(LiteralString)
  if l.is_a?(Integer)
    raise(Error, 'Limits must be greater than or equal to 1') unless l >= 1
  end

  ds = clone(:limit=>l)
  ds = ds.offset(o) unless no_offset
  ds
end

- (Object) 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.



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# File 'lib/sequel/dataset/sql.rb', line 75

def literal_append(sql, v)
  case v
  when Symbol
    literal_symbol_append(sql, v)
  when String
    case v
    when LiteralString
      sql << v
    when SQL::Blob
      literal_blob_append(sql, v)
    else
      literal_string_append(sql, v)
    end
  when Integer
    sql << literal_integer(v)
  when Hash
    literal_hash_append(sql, v)
  when SQL::Expression
    literal_expression_append(sql, v)
  when Float
    sql << literal_float(v)
  when BigDecimal
    sql << literal_big_decimal(v)
  when NilClass
    sql << literal_nil
  when TrueClass
    sql << literal_true
  when FalseClass
    sql << literal_false
  when Array
    literal_array_append(sql, v)
  when Time
    sql << (v.is_a?(SQLTime) ? literal_sqltime(v) : literal_time(v))
  when DateTime
    sql << literal_datetime(v)
  when Date
    sql << literal_date(v)
  when Dataset
    literal_dataset_append(sql, v)
  else
    literal_other_append(sql, v)
  end
end

- (Object) lock_style(style)

Returns a cloned dataset with the given lock style. If style is a string, it will be used directly. You should never pass a string to this method that is derived from user input, as that can lead to SQL injection.

A symbol may be used for database independent locking behavior, but all supported symbols have separate methods (e.g. for_update).

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


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# File 'lib/sequel/dataset/query.rb', line 550

def lock_style(style)
  clone(:lock => style)
end

- (Object) 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'], ...]


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# File 'lib/sequel/dataset/actions.rb', line 383

def map(column=nil, &block)
  if column
    raise(Error, ARG_BLOCK_ERROR_MSG) if block
    return naked.map(column) if row_proc
    if column.is_a?(Array)
      super(){|r| r.values_at(*column)}
    else
      super(){|r| r[column]}
    end
  else
    super(&block)
  end
end

- (Object) max(column = Sequel.virtual_row(&Proc.new))

Returns the maximum value for the given column/expression. Uses a virtual row block if no argument is given.

DB[:table].max(:id) # SELECT max(id) FROM table LIMIT 1
# => 10
DB[:table].max{function(column)} # SELECT max(function(column)) FROM table LIMIT 1
# => 7


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# File 'lib/sequel/dataset/actions.rb', line 404

def max(column=Sequel.virtual_row(&Proc.new))
  aggregate_dataset.get{max(column).as(:max)}
end

- (Object) min(column = Sequel.virtual_row(&Proc.new))

Returns the minimum value for the given column/expression. Uses a virtual row block if no argument is given.

DB[:table].min(:id) # SELECT min(id) FROM table LIMIT 1
# => 1
DB[:table].min{function(column)} # SELECT min(function(column)) FROM table LIMIT 1
# => 0


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# File 'lib/sequel/dataset/actions.rb', line 415

def min(column=Sequel.virtual_row(&Proc.new))
  aggregate_dataset.get{min(column).as(:min)}
end

- (Object) multi_insert(hashes, opts = 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.



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# File 'lib/sequel/dataset/actions.rb', line 431

def multi_insert(hashes, opts=OPTS)
  return if hashes.empty?
  columns = hashes.first.keys
  import(columns, hashes.map{|h| columns.map{|c| h[c]}}, opts)
end

- (Object) 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.



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# File 'lib/sequel/dataset/sql.rb', line 125

def multi_insert_sql(columns, values)
  values.map{|r| insert_sql(columns, r)}
end

- (Object) 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}]


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# File 'lib/sequel/dataset/query.rb', line 560

def naked
  ds = clone
  ds.row_proc = nil
  ds
end

- (Object) naked!

Remove the row_proc from the current dataset.



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# File 'lib/sequel/dataset/mutation.rb', line 71

def naked!
  raise_if_frozen!
  self.row_proc = nil
  self
end

- (Object) negative_boolean_constant_sql_append(sql, constant)

SQL fragment for NegativeBooleanConstants



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# File 'lib/sequel/dataset/sql.rb', line 513

def negative_boolean_constant_sql_append(sql, constant)
  sql << NOT_SPACE
  boolean_constant_sql_append(sql, constant)
end

- (Object) offset(o)

Returns a copy of the dataset with a specified order. Can be safely combined with limit. If you call limit with an offset, it will override override the offset if you've called offset first.

DB[:items].offset(10) # SELECT * FROM items OFFSET 10


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# File 'lib/sequel/dataset/query.rb', line 571

def offset(o)
  o = o.to_i if o.is_a?(String) && !o.is_a?(LiteralString)
  if o.is_a?(Integer)
    raise(Error, 'Offsets must be greater than or equal to 0') unless o >= 0
  end
  clone(:offset => o)
end

- (Object) or(*cond, &block)

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

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


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# File 'lib/sequel/dataset/query.rb', line 583

def or(*cond, &block)
  cond = cond.first if cond.size == 1
  v = @opts[:where]
  if v.nil? || (cond.respond_to?(:empty?) && cond.empty? && !block)
    clone
  else
    clone(:where => SQL::BooleanExpression.new(:OR, v, filter_expr(cond, &block)))
  end
end

- (Object) 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 where.

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(Sequel.lit('a + b')) # SELECT * FROM items ORDER BY a + b
DB[:items].order(:a + :b) # SELECT * FROM items ORDER BY (a + b)
DB[:items].order(Sequel.desc(:name)) # SELECT * FROM items ORDER BY name DESC
DB[:items].order(Sequel.asc(:name, :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


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# File 'lib/sequel/dataset/query.rb', line 607

def order(*columns, &block)
  virtual_row_columns(columns, block)
  clone(:order => (columns.compact.empty?) ? nil : columns)
end

- (Object) order_append(*columns, &block)

Alias of order_more, for naming consistency with order_prepend.



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# File 'lib/sequel/dataset/query.rb', line 613

def order_append(*columns, &block)
  order_more(*columns, &block)
end

- (Object) order_by(*columns, &block)

Alias of order



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# File 'lib/sequel/dataset/query.rb', line 618

def order_by(*columns, &block)
  order(*columns, &block)
end

- (Object) 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


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# File 'lib/sequel/dataset/query.rb', line 627

def order_more(*columns, &block)
  columns = @opts[:order] + columns if @opts[:order]
  order(*columns, &block)
end

- (Object) 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


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# File 'lib/sequel/dataset/query.rb', line 637

def order_prepend(*columns, &block)
  ds = order(*columns, &block)
  @opts[:order] ? ds.order_more(*@opts[:order]) : ds
end

- (Object) ordered_expression_sql_append(sql, oe)

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



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# File 'lib/sequel/dataset/sql.rb', line 520

def ordered_expression_sql_append(sql, oe)
  literal_append(sql, oe.expression)
  sql << (oe.descending ? DESC : ASC)
  case oe.nulls
  when :first
    sql << NULLS_FIRST
  when :last
    sql << NULLS_LAST
  end
end

- (Object) paged_each(opts = OPTS)

Yields each row in the dataset, but interally uses multiple queries as needed to process the entire result set without keeping all rows in the dataset in memory, even if the underlying driver buffers all query results in memory.

Because this uses multiple queries internally, in order to remain consistent, it also uses a transaction internally. Additionally, to work correctly, the dataset must have unambiguous order. Using an ambiguous order can result in an infinite loop, as well as subtler bugs such as yielding duplicate rows or rows being skipped.

Sequel checks that the datasets using this method have an order, but it cannot ensure that the order is unambiguous.

Options:

:rows_per_fetch

The number of rows to fetch per query. Defaults to 1000.

:strategy

The strategy to use for paging of results. By default this is :offset, for using an approach with a limit and offset for every page. This can be set to :filter, which uses a limit and a filter that excludes rows from previous pages. In order for this strategy to work, you must be selecting the columns you are ordering by, and non of the columns can contain NULLs. Note that some Sequel adapters have optimized implementations that will use cursors or streaming regardless of the :strategy option used.

:filter_values

If the :strategy=>:filter option is used, this option should be a proc that accepts the last retreived row for the previous page and an array of ORDER BY expressions, and returns an array of values relating to those expressions for the last retrieved row. You will need to use this option if your ORDER BY expressions are not simple columns, if they contain qualified identifiers that would be ambiguous unqualified, if they contain any identifiers that are aliased in SELECT, and potentially other cases.

Examples:

DB[:table].order(:id).paged_each{|row| ...}
# SELECT * FROM table ORDER BY id LIMIT 1000
# SELECT * FROM table ORDER BY id LIMIT 1000 OFFSET 1000
# ...

DB[:table].order(:id).paged_each(:rows_per_fetch=>100){|row| ...}
# SELECT * FROM table ORDER BY id LIMIT 100
# SELECT * FROM table ORDER BY id LIMIT 100 OFFSET 100
# ...

DB[:table].order(:id).paged_each(:strategy=>:filter){|row| ...}
# SELECT * FROM table ORDER BY id LIMIT 1000
# SELECT * FROM table WHERE id > 1001 ORDER BY id LIMIT 1000
# ...

DB[:table].order(:table__id).paged_each(:strategy=>:filter,
  :filter_values=>proc{|row, exprs| [row[:id]]}){|row| ...}
# SELECT * FROM table ORDER BY id LIMIT 1000
# SELECT * FROM table WHERE id > 1001 ORDER BY id LIMIT 1000
# ...


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# File 'lib/sequel/dataset/actions.rb', line 488

def paged_each(opts=OPTS)
  unless @opts[:order]
    raise Sequel::Error, "Dataset#paged_each requires the dataset be ordered"
  end

  total_limit = @opts[:limit]
  offset = @opts[:offset]
  if server = @opts[:server]
    opts = opts.merge(:server=>server)
  end

  rows_per_fetch = opts[:rows_per_fetch] || 1000
  strategy = if offset || total_limit
    :offset
  else
    opts[:strategy] || :offset
  end

  db.transaction(opts) do
    case strategy
    when :filter
      filter_values = opts[:filter_values] || proc{|row, exprs| exprs.map{|e| row[hash_key_symbol(e)]}}
      base_ds = ds = limit(rows_per_fetch)
      while ds
        last_row = nil
        ds.each do |row|
          last_row = row
          yield row
        end
        ds = (base_ds.where(ignore_values_preceding(last_row, &filter_values)) if last_row)
      end
    else
      offset ||= 0
      num_rows_yielded = rows_per_fetch
      total_rows = 0

      while num_rows_yielded == rows_per_fetch && (total_limit.nil? || total_rows < total_limit)
        if total_limit && total_rows + rows_per_fetch > total_limit
          rows_per_fetch = total_limit - total_rows
        end

        num_rows_yielded = 0
        limit(rows_per_fetch, offset).each do |row|
          num_rows_yielded += 1
          total_rows += 1 if total_limit
          yield row
        end

        offset += rows_per_fetch
      end
    end
  end

  self
end

- (Object) placeholder_literal_string_sql_append(sql, pls)

SQL fragment for a literal string with placeholders



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# File 'lib/sequel/dataset/sql.rb', line 532

def placeholder_literal_string_sql_append(sql, pls)
  args = pls.args
  str = pls.str
  sql << PAREN_OPEN if pls.parens
  if args.is_a?(Hash)
    if args.empty?
      sql << str
    else
      re = /:(#{args.keys.map{|k| Regexp.escape(k.to_s)}.join('|')})\b/
      loop do
        previous, q, str = str.partition(re)
        sql << previous
        literal_append(sql, args[($1||q[1..-1].to_s).to_sym]) unless q.empty?
        break if str.empty?
      end
    end
  elsif str.is_a?(Array)
    len = args.length
    str.each_with_index do |s, i|
      sql << s
      literal_append(sql, args[i]) unless i == len
    end
    unless str.length == args.length || str.length == args.length + 1
      raise Error, "Mismatched number of placeholders (#{str.length}) and placeholder arguments (#{args.length}) when using placeholder array"
    end
  else
    i = -1
    match_len = args.length - 1
    loop do
      previous, q, str = str.partition(QUESTION_MARK)
      sql << previous
      literal_append(sql, args.at(i+=1)) unless q.empty?
      if str.empty?
        unless i == match_len
          raise Error, "Mismatched number of placeholders (#{i+1}) and placeholder arguments (#{args.length}) when using placeholder array"
        end
        break
      end
    end
  end
  sql << PAREN_CLOSE if pls.parens
end

- (Object) 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


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# File 'lib/sequel/dataset/prepared_statements.rb', line 250

def prepare(type, name=nil, *values)
  ps = to_prepared_statement(type, values)
  db.set_prepared_statement(name, ps) if name
  ps
end

- (Boolean) 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.

Returns:

  • (Boolean)


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# File 'lib/sequel/dataset/features.rb', line 21

def provides_accurate_rows_matched?
  true
end

- (Object) qualified_identifier_sql_append(sql, table, column = (c = table.column; table = table.table; c))

SQL fragment for the qualifed identifier, specifying a table and a column (or schema and table). If 3 arguments are given, the 2nd should be the table/qualifier and the third should be column/qualified. If 2 arguments are given, the 2nd should be an SQL::QualifiedIdentifier.



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# File 'lib/sequel/dataset/sql.rb', line 579

def qualified_identifier_sql_append(sql, table, column=(c = table.column; table = table.table; c))
  identifier_append(sql, table)
  sql << DOT
  identifier_append(sql, column)
end

- (Object) qualify(table = first_source)

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

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

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


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# File 'lib/sequel/dataset/query.rb', line 649

def qualify(table=first_source)
  o = @opts
  return clone if o[:sql]
  h = {}
  (o.keys & QUALIFY_KEYS).each do |k|
    h[k] = qualified_expression(o[k], table)
  end
  h[:select] = [SQL::ColumnAll.new(table)] if !o[:select] || o[:select].empty?
  clone(h)
end

- (Object) 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.



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# File 'lib/sequel/dataset/sql.rb', line 588

def quote_identifier_append(sql, name)
  if name.is_a?(LiteralString)
    sql << name
  else
    name = name.value if name.is_a?(SQL::Identifier)
    name = input_identifier(name)
    if quote_identifiers?
      quoted_identifier_append(sql, name)
    else
      sql << name
    end
  end
end

- (Object) quote_identifiers=(v)

Set whether to quote identifiers for this dataset



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# File 'lib/sequel/dataset/mutation.rb', line 78

def quote_identifiers=(v)
  raise_if_frozen!
  @quote_identifiers = v
end

- (Boolean) quote_identifiers?

Whether this dataset quotes identifiers.

Returns:

  • (Boolean)


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# File 'lib/sequel/dataset/features.rb', line 10

def quote_identifiers?
  if defined?(@quote_identifiers)
    @quote_identifiers
  else
    @quote_identifiers = db.quote_identifiers?
  end
end

- (Object) quote_schema_table_append(sql, table)

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



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# File 'lib/sequel/dataset/sql.rb', line 604

def quote_schema_table_append(sql, table)
  schema, table = schema_and_table(table)
  if schema
    quote_identifier_append(sql, schema)
    sql << DOT
  end
  quote_identifier_append(sql, table)
end

- (Object) 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).



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# File 'lib/sequel/dataset/sql.rb', line 616

def quoted_identifier_append(sql, name)
  sql << QUOTE << name.to_s.gsub(QUOTE_RE, DOUBLE_QUOTE) << QUOTE
end

- (Object) range(column = Sequel.virtual_row(&Proc.new))

Returns a Range instance made from the minimum and maximum values for the given column/expression. Uses a virtual row block if no argument is given.

DB[:table].range(:id) # SELECT max(id) AS v1, min(id) AS v2 FROM table LIMIT 1
# => 1..10
DB[:table].interval{function(column)} # SELECT max(function(column)) AS v1, min(function(column)) AS v2 FROM table LIMIT 1
# => 0..7


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# File 'lib/sequel/dataset/actions.rb', line 551

def range(column=Sequel.virtual_row(&Proc.new))
  if r = aggregate_dataset.select{[min(column).as(v1), max(column).as(v2)]}.first
    (r[:v1]..r[:v2])
  end
end

- (Boolean) recursive_cte_requires_column_aliases?

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

Returns:

  • (Boolean)


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# File 'lib/sequel/dataset/features.rb', line 27

def recursive_cte_requires_column_aliases?
  false
end

- (Boolean) requires_placeholder_type_specifiers?

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

Returns:

  • (Boolean)


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# File 'lib/sequel/dataset/features.rb', line 39

def requires_placeholder_type_specifiers?
  false
end

- (Boolean) requires_sql_standard_datetimes?

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

Returns:

  • (Boolean)


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# File 'lib/sequel/dataset/features.rb', line 33

def requires_sql_standard_datetimes?
  false
end

- (Object) 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


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# File 'lib/sequel/dataset/query.rb', line 668

def returning(*values)
  clone(:returning=>values)
end

- (Object) reverse(*order, &block)

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].reverse{foo(bar)} # SELECT * FROM items ORDER BY foo(bar) DESC
DB[:items].order(:id).reverse # SELECT * FROM items ORDER BY id DESC
DB[:items].order(:id).reverse(Sequel.desc(:name)) # SELECT * FROM items ORDER BY name ASC


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# File 'lib/sequel/dataset/query.rb', line 679

def reverse(*order, &block)
  virtual_row_columns(order, block)
  order(*invert_order(order.empty? ? @opts[:order] : order))
end

- (Object) reverse_order(*order, &block)

Alias of reverse



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# File 'lib/sequel/dataset/query.rb', line 685

def reverse_order(*order, &block)
  reverse(*order, &block)
end

- (Object) row_number_column

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



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# File 'lib/sequel/dataset/misc.rb', line 168

def row_number_column
  :x_sequel_row_number_x
end

- (Object) schema_and_table(table_name, sch = nil)

Split the schema information from the table, returning two strings, one for the schema and one for the table. The returned schema may be nil, but the table will always have a string value.

Note that this function does not handle tables with more than one level of qualification (e.g. database.schema.table on Microsoft SQL Server).



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# File 'lib/sequel/dataset/sql.rb', line 627

def schema_and_table(table_name, sch=nil)
  sch = sch.to_s if sch
  case table_name
  when Symbol
    s, t, _ = split_symbol(table_name)
    [s||sch, t]
  when SQL::QualifiedIdentifier
    [table_name.table.to_s, table_name.column.to_s]
  when SQL::Identifier
    [sch, table_name.value.to_s]
  when String
    [sch, table_name]
  else
    raise Error, 'table_name should be a Symbol, SQL::QualifiedIdentifier, SQL::Identifier, or String'
  end
end

- (Object) 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 where.

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


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# File 'lib/sequel/dataset/query.rb', line 696

def select(*columns, &block)
  virtual_row_columns(columns, block)
  clone(:select => columns)
end

- (Object) 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


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# File 'lib/sequel/dataset/query.rb', line 708

def select_all(*tables)
  if tables.empty?
    clone(:select => nil)
  else
    select(*tables.map{|t| i, a = split_alias(t); a || i}.map{|t| SQL::ColumnAll.new(t)})
  end
end

- (Object) 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


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# File 'lib/sequel/dataset/query.rb', line 723

def select_append(*columns, &block)
  cur_sel = @opts[:select]
  if !cur_sel || cur_sel.empty?
    unless supports_select_all_and_column?
      return select_all(*(Array(@opts[:from]) + Array(@opts[:join]))).select_more(*columns, &block)
    end
    cur_sel = [WILDCARD]
  end
  select(*(cur_sel + columns), &block)
end

- (Object) 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 where.

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)


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# File 'lib/sequel/dataset/query.rb', line 743

def select_group(*columns, &block)
  virtual_row_columns(columns, block)
  select(*columns).group(*columns.map{|c| unaliased_identifier(c)})
end

- (Object) 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 columns given.

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.



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# File 'lib/sequel/dataset/actions.rb', line 572

def select_hash(key_column, value_column)
  _select_hash(:to_hash, key_column, value_column)
end

- (Object) select_hash_groups(key_column, value_column)

Returns a hash with key_column values as keys and an array of value_column values. Similar to to_hash_groups, but only selects the columns given.

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

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

DB[:table].select_hash([:first, :middle], [:last, :id]) # SELECT * FROM table
# {['a', 'b']=>[['c', 1], ['d', 2], ...], ...}

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.



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# File 'lib/sequel/dataset/actions.rb', line 591

def select_hash_groups(key_column, value_column)
  _select_hash(:to_hash_groups, key_column, value_column)
end

- (Object) 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.



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# File 'lib/sequel/dataset/actions.rb', line 615

def select_map(column=nil, &block)
  _select_map(column, false, &block)
end

- (Object) select_more(*columns, &block)

Alias for select_append.



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# File 'lib/sequel/dataset/query.rb', line 749

def select_more(*columns, &block)
  select_append(*columns, &block)
end

- (Object) 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.



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# File 'lib/sequel/dataset/actions.rb', line 635

def select_order_map(column=nil, &block)
  _select_map(column, true, &block)
end

- (Object) select_sql

Returns a SELECT SQL query string.

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


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# File 'lib/sequel/dataset/sql.rb', line 132

def select_sql
  return static_sql(@opts[:sql]) if @opts[:sql]
  clause_sql(:select)
end

- (Object) 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


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# File 'lib/sequel/dataset/query.rb', line 762

def server(servr)
  clone(:server=>servr)
end

- (Object) 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 ...


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# File 'lib/sequel/dataset/graph.rb', line 225

def set_graph_aliases(graph_aliases)
  columns, graph_aliases = graph_alias_columns(graph_aliases)
  ds = select(*columns)
  ds.opts[:graph_aliases] = graph_aliases
  ds
end

- (Object) 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.



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# File 'lib/sequel/dataset/actions.rb', line 642

def single_record
  clone(:limit=>1).each{|r| return r}
  nil
end

- (Object) 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.



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# File 'lib/sequel/dataset/actions.rb', line 650

def single_value
  if r = ungraphed.naked.single_record
    r.values.first
  end
end

- (Object) 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.



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# File 'lib/sequel/dataset/misc.rb', line 175

def split_alias(c)
  case c
  when Symbol
    c_table, column, aliaz = split_symbol(c)
    [c_table ? SQL::QualifiedIdentifier.new(c_table, column.to_sym) : column.to_sym, aliaz]
  when SQL::AliasedExpression
    [c.expression, c.alias]
  when SQL::JoinClause
    [c.table, c.table_alias]
  else
    [c, nil]
  end
end

- (Object) split_qualifiers(table_name, *args)

Splits table_name into an array of strings.

ds.split_qualifiers(:s) # ['s']
ds.split_qualifiers(:t__s) # ['t', 's']
ds.split_qualifiers(Sequel.qualify(:d, :t__s)) # ['d', 't', 's']
ds.split_qualifiers(Sequel.qualify(:h__d, :t__s)) # ['h', 'd', 't', 's']


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# File 'lib/sequel/dataset/sql.rb', line 650

def split_qualifiers(table_name, *args)
  case table_name
  when SQL::QualifiedIdentifier
    split_qualifiers(table_name.table, nil) + split_qualifiers(table_name.column, nil)
  else
    sch, table = schema_and_table(table_name, *args)
    sch ? [sch, table] : [table]
  end
end

- (Object) sql

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



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# File 'lib/sequel/dataset/sql.rb', line 138

def sql
  select_sql
end

- (Object) subscript_sql_append(sql, s)

SQL fragment for specifying subscripts (SQL array accesses)



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# File 'lib/sequel/dataset/sql.rb', line 661

def subscript_sql_append(sql, s)
  literal_append(sql, s.f)
  sql << BRACKET_OPEN
  if s.sub.length == 1 && (range = s.sub.first).is_a?(Range)
    literal_append(sql, range.begin)
    sql << COLON
    e = range.end
    e -= 1 if range.exclude_end? && e.is_a?(Integer)
    literal_append(sql, e)
  else
    expression_list_append(sql, s.sub)
  end
  sql << BRACKET_CLOSE
end

- (Object) sum(column = Sequel.virtual_row(&Proc.new))

Returns the sum for the given column/expression. Uses a virtual row block if no column is given.

DB[:table].sum(:id) # SELECT sum(id) FROM table LIMIT 1
# => 55
DB[:table].sum{function(column)} # SELECT sum(function(column)) FROM table LIMIT 1
# => 10


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# File 'lib/sequel/dataset/actions.rb', line 663

def sum(column=Sequel.virtual_row(&Proc.new))
  aggregate_dataset.get{sum(column).as(:sum)}
end

- (Boolean) 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.

Returns:

  • (Boolean)


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# File 'lib/sequel/dataset/features.rb', line 46

def supports_cte?(type=:select)
  send(:#{type}_clause_methods").include?(:#{type}_with_sql")
end

- (Boolean) 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.

Returns:

  • (Boolean)


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# File 'lib/sequel/dataset/features.rb', line 53

def supports_cte_in_subqueries?
  false
end

- (Boolean) supports_distinct_on?

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

Returns:

  • (Boolean)


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# File 'lib/sequel/dataset/features.rb', line 58

def supports_distinct_on?
  false
end

- (Boolean) supports_group_cube?

Whether the dataset supports CUBE with GROUP BY.

Returns:

  • (Boolean)


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# File 'lib/sequel/dataset/features.rb', line 63

def supports_group_cube?
  false
end

- (Boolean) supports_group_rollup?

Whether the dataset supports ROLLUP with GROUP BY.

Returns:

  • (Boolean)


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# File 'lib/sequel/dataset/features.rb', line 68

def supports_group_rollup?
  false
end

- (Boolean) supports_insert_select?

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

Returns:

  • (Boolean)


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# File 'lib/sequel/dataset/features.rb', line 74

def supports_insert_select?
  supports_returning?(:insert)
end

- (Boolean) supports_intersect_except?

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

Returns:

  • (Boolean)


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# File 'lib/sequel/dataset/features.rb', line 79

def supports_intersect_except?
  true
end

- (Boolean) supports_intersect_except_all?

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

Returns:

  • (Boolean)


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# File 'lib/sequel/dataset/features.rb', line 84

def supports_intersect_except_all?
  true
end

- (Boolean) supports_is_true?

Whether the dataset supports the IS TRUE syntax.

Returns:

  • (Boolean)


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# File 'lib/sequel/dataset/features.rb', line 89

def supports_is_true?
  true
end

- (Boolean) supports_join_using?

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

Returns:

  • (Boolean)


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# File 'lib/sequel/dataset/features.rb', line 94

def supports_join_using?
  true
end

- (Boolean) supports_lateral_subqueries?

Whether the dataset supports LATERAL for subqueries in the FROM or JOIN clauses.

Returns:

  • (Boolean)


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# File 'lib/sequel/dataset/features.rb', line 99

def supports_lateral_subqueries?
  false
end

- (Boolean) supports_modifying_joins?

Whether modifying joined datasets is supported.

Returns:

  • (Boolean)


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# File 'lib/sequel/dataset/features.rb', line 104

def supports_modifying_joins?
  false
end

- (Boolean) supports_multiple_column_in?

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

Returns:

  • (Boolean)


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# File 'lib/sequel/dataset/features.rb', line 110

def supports_multiple_column_in?
  true
end

- (Boolean) 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

Returns:

  • (Boolean)


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# File 'lib/sequel/dataset/features.rb', line 116

def supports_ordered_distinct_on?
  supports_distinct_on?
end

- (Boolean) supports_regexp?

Whether the dataset supports pattern matching by regular expressions.

Returns:

  • (Boolean)


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# File 'lib/sequel/dataset/features.rb', line 121

def supports_regexp?
  false
end

- (Boolean) supports_replace?

Whether the dataset supports REPLACE syntax, false by default.

Returns:

  • (Boolean)


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# File 'lib/sequel/dataset/features.rb', line 126

def supports_replace?
  false
end

- (Boolean) supports_returning?(type)

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

Returns:

  • (Boolean)


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# File 'lib/sequel/dataset/features.rb', line 132

def supports_returning?(type)
  send(:#{type}_clause_methods").include?(:#{type}_returning_sql")
end

- (Boolean) supports_select_all_and_column?

Whether the database supports SELECT *, column FROM table

Returns:

  • (Boolean)


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# File 'lib/sequel/dataset/features.rb', line 137

def supports_select_all_and_column?
  true
end

- (Boolean) supports_timestamp_timezones?

Whether the dataset supports timezones in literal timestamps

Returns:

  • (Boolean)


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# File 'lib/sequel/dataset/features.rb', line 142

def supports_timestamp_timezones?
  false
end

- (Boolean) supports_timestamp_usecs?

Whether the dataset supports fractional seconds in literal timestamps

Returns:

  • (Boolean)


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# File 'lib/sequel/dataset/features.rb', line 147

def supports_timestamp_usecs?
  true
end

- (Boolean) supports_where_true?

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

Returns:

  • (Boolean)


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# File 'lib/sequel/dataset/features.rb', line 158

def supports_where_true?
  true
end

- (Boolean) supports_window_functions?

Whether the dataset supports window functions.

Returns:

  • (Boolean)


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# File 'lib/sequel/dataset/features.rb', line 152

def supports_window_functions?
  false
end

- (Object) 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'}, ...}


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# File 'lib/sequel/dataset/actions.rb', line 686

def to_hash(key_column, value_column = nil)
  h = {}
  if value_column
    return naked.to_hash(key_column, value_column) if row_proc
    if value_column.is_a?(Array)
      if key_column.is_a?(Array)
        each{|r| h[r.values_at(*key_column)] = r.values_at(*value_column)}
      else
        each{|r| h[r[key_column]] = r.values_at(*value_column)}
      end
    else
      if key_column.is_a?(Array)
        each{|r| h[r.values_at(*key_column)] = r[value_column]}
      else
        each{|r| h[r[key_column]] = r[value_column]}
      end
    end
  elsif key_column.is_a?(Array)
    each{|r| h[r.values_at(*key_column)] = r}
  else
    each{|r| h[r[key_column]] = r}
  end
  h
end

- (Object) to_hash_groups(key_column, value_column = nil)

Returns a hash with one column used as key and the values being an array of column values. If the value_column is not given or nil, uses the entire hash as the value.

DB[:table].to_hash(:name, :id) # SELECT * FROM table
# {'Jim'=>[1, 4, 16, ...], 'Bob'=>[2], ...}

DB[:table].to_hash(:name) # SELECT * FROM table
# {'Jim'=>[{:id=>1, :name=>'Jim'}, {:id=>4, :name=>'Jim'}, ...], 'Bob'=>[{: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([:first, :middle], [:last, :id]) # SELECT * FROM table
# {['Jim', 'Bob']=>[['Smith', 1], ['Jackson', 4], ...], ...}

DB[:table].to_hash([:first, :middle]) # SELECT * FROM table
# {['Jim', 'Bob']=>[{:id=>1, :first=>'Jim', :middle=>'Bob', :last=>'Smith'}, ...], ...}


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# File 'lib/sequel/dataset/actions.rb', line 729

def to_hash_groups(key_column, value_column = nil)
  h = {}
  if value_column
    return naked.to_hash_groups(key_column, value_column) if row_proc
    if value_column.is_a?(Array)
      if key_column.is_a?(Array)
        each{|r| (h[r.values_at(*key_column)] ||= []) << r.values_at(*value_column)}
      else
        each{|r| (h[r[key_column]] ||= []) << r.values_at(*value_column)}
      end
    else
      if key_column.is_a?(Array)
        each{|r| (h[r.values_at(*key_column)] ||= []) << r[value_column]}
      else
        each{|r| (h[r[key_column]] ||= []) << r[value_column]}
      end
    end
  elsif key_column.is_a?(Array)
    each{|r| (h[r.values_at(*key_column)] ||= []) << r}
  else
    each{|r| (h[r[key_column]] ||= []) << r}
  end
  h
end

- (Object) truncate

Truncates the dataset. Returns nil.

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


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# File 'lib/sequel/dataset/actions.rb', line 758

def truncate
  execute_ddl(truncate_sql)
end

- (Object) truncate_sql

Returns a TRUNCATE SQL query string. See truncate

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


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# File 'lib/sequel/dataset/sql.rb', line 145

def truncate_sql
  if opts[:sql]
    static_sql(opts[:sql])
  else
    check_truncation_allowed!
    raise(InvalidOperation, "Can't truncate filtered datasets") if opts[:where] || opts[:having]
    t = ''
    source_list_append(t, opts[:from])
    _truncate_sql(t)
  end
end

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


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# File 'lib/sequel/dataset/query.rb', line 776

def unbind
  u = Unbinder.new
  ds = clone(:where=>u.transform(opts[:where]), :join=>u.transform(opts[:join]))
  [ds, u.binds]
end

- (Object) 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


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# File 'lib/sequel/dataset/query.rb', line 786

def unfiltered
  clone(:where => nil, :having => nil)
end

- (Object) ungraphed

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



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# File 'lib/sequel/dataset/graph.rb', line 234

def ungraphed
  clone(:graph=>nil, :graph_aliases=>nil)
end

- (Object) 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


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# File 'lib/sequel/dataset/query.rb', line 794

def ungrouped
  clone(:group => nil, :having => nil)
end

- (Object) union(dataset, opts = 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


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# File 'lib/sequel/dataset/query.rb', line 814

def union(dataset, opts=OPTS)
  compound_clone(:union, dataset, opts)
end

- (Object) unlimited

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

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


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# File 'lib/sequel/dataset/query.rb', line 821

def unlimited
  clone(:limit=>nil, :offset=>nil)
end

- (Object) unordered

Returns a copy of the dataset with no order.

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


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# File 'lib/sequel/dataset/query.rb', line 828

def unordered
  order(nil)
end

- (Object) 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


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# File 'lib/sequel/dataset/misc.rb', line 211

def unused_table_alias(table_alias, used_aliases = [])
  table_alias = alias_symbol(table_alias)
  used_aliases += opts[:from].map{|t| alias_symbol(t)} if opts[:from]
  used_aliases += opts[:join].map{|j| j.table_alias ? alias_alias_symbol(j.table_alias) : alias_symbol(j.table)} if opts[:join]
  if used_aliases.include?(table_alias)
    i = 0
    loop do
      ta = :#{table_alias}_#{i}"
      return ta unless used_aliases.include?(ta)
      i += 1 
    end
  else
    table_alias
  end
end

- (Object) update(values = OPTS, &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


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# File 'lib/sequel/dataset/actions.rb', line 772

def update(values=OPTS, &block)
  sql = update_sql(values)
  if uses_returning?(:update)
    returning_fetch_rows(sql, &block)
  else
    execute_dui(sql)
  end
end

- (Object) update_sql(values = OPTS)

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.



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# File 'lib/sequel/dataset/sql.rb', line 164

def update_sql(values = OPTS)
  return static_sql(opts[:sql]) if opts[:sql]
  check_modification_allowed!
  clone(:values=>values)._update_sql
end

- (Object) where(*cond, &block)

Returns a copy of the dataset with the given WHERE conditions imposed upon it.

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.

where also accepts 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].where(:id => 3)
# SELECT * FROM items WHERE (id = 3)

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

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

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

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

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

Multiple where calls can be chained for scoping:

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

See the “Dataset Filtering” guide for more examples and details.



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# File 'lib/sequel/dataset/query.rb', line 882

def where(*cond, &block)
  _filter(:where, *cond, &block)
end

- (Object) window_function_sql_append(sql, function, window)

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



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# File 'lib/sequel/dataset/sql.rb', line 718

def window_function_sql_append(sql, function, window)
  literal_append(sql, function)
  sql << OVER
  literal_append(sql, window)
end

- (Object) window_sql_append(sql, opts)

The SQL fragment for the given window's options.

Raises:



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# File 'lib/sequel/dataset/sql.rb', line 677

def window_sql_append(sql, opts)
  raise(Error, 'This dataset does not support window functions') unless supports_window_functions?
  sql << PAREN_OPEN
  window, part, order, frame = opts.values_at(:window, :partition, :order, :frame)
  space = false
  space_s = SPACE
  if window
    literal_append(sql, window)
    space = true
  end
  if part
    sql << space_s if space
    sql << PARTITION_BY
    expression_list_append(sql, Array(part))
    space = true
  end
  if order
    sql << space_s if space
    sql << ORDER_BY_NS
    expression_list_append(sql, Array(order))
    space = true
  end
  case frame
    when nil
      # nothing
    when :all
      sql << space_s if space
      sql << FRAME_ALL
    when :rows
      sql << space_s if space
      sql << FRAME_ROWS
    when String
      sql << space_s if space
      sql << frame
    else
      raise Error, "invalid window frame clause, should be :all, :rows, a string, or nil"
  end
  sql << PAREN_CLOSE
end

- (Object) with(name, dataset, opts = 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].where(:name.like('A%')))
# WITH items AS (SELECT * FROM syx WHERE (name LIKE 'A%')) SELECT * FROM items

Raises:



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# File 'lib/sequel/dataset/query.rb', line 894

def with(name, dataset, opts=OPTS)
  raise(Error, 'This datatset does not support common table expressions') unless supports_cte?
  if hoist_cte?(dataset)
    s, ds = hoist_cte(dataset)
    s.with(name, ds, opts)
  else
    clone(:with=>(@opts[:with]||[]) + [opts.merge(:name=>name, :dataset=>dataset)])
  end
end

- (Object) with_recursive(name, nonrecursive, recursive, opts = 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].with_recursive(:t,
  DB[:i1].select(:id, :parent_id).where(:parent_id=>nil),
  DB[:i1].join(:t, :id=>:parent_id).select(:i1__id, :i1__parent_id),
  :args=>[:id, :parent_id])

# WITH RECURSIVE "t"("id", "parent_id") AS (
#   SELECT "id", "parent_id" FROM "i1" WHERE ("parent_id" IS NULL)
#   UNION ALL
#   SELECT "i1"."id", "i1"."parent_id" FROM "i1" INNER JOIN "t" ON ("t"."id" = "i1"."parent_id")
# ) SELECT * FROM "t"

Raises:



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# File 'lib/sequel/dataset/query.rb', line 920

def with_recursive(name, nonrecursive, recursive, opts=OPTS)
  raise(Error, 'This datatset does not support common table expressions') unless supports_cte?
  if hoist_cte?(nonrecursive)
    s, ds = hoist_cte(nonrecursive)
    s.with_recursive(name, ds, recursive, opts)
  elsif hoist_cte?(recursive)
    s, ds = hoist_cte(recursive)
    s.with_recursive(name, nonrecursive, ds, opts)
  else
    clone(:with=>(@opts[:with]||[]) + [opts.merge(:recursive=>true, :name=>name, :dataset=>nonrecursive.union(recursive, {:all=>opts[:union_all] != false, :from_self=>false}))])
  end
end

- (Object) 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)


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# File 'lib/sequel/dataset/query.rb', line 945

def with_sql(sql, *args)
  if sql.is_a?(Symbol)
    sql = send(sql, *args)
  else
    sql = SQL::PlaceholderLiteralString.new(sql, args) unless args.empty?
  end
  clone(:sql=>sql)
end

- (Object) with_sql_delete(sql)

Execute the given SQL and return the number of rows deleted. This exists solely as an optimization, replacing with_sql(sql).delete. It's significantly faster as it does not require cloning the current dataset.



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# File 'lib/sequel/dataset/actions.rb', line 784

def with_sql_delete(sql)
  execute_dui(sql)
end