Class: Sequel::Dataset

Inherits:
Object show all
Extended by:
Metaprogramming
Includes:
Enumerable, Metaprogramming, 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/features.rb,
lib/sequel/dataset/mutation.rb,
lib/sequel/extensions/query.rb,
lib/sequel/extensions/to_dot.rb,
lib/sequel/extensions/pagination.rb,
lib/sequel/extensions/null_dataset.rb,
lib/sequel/extensions/pretty_table.rb,
lib/sequel/extensions/select_remove.rb,
lib/sequel/dataset/prepared_statements.rb,
lib/sequel/adapters/utils/stored_procedures.rb,
lib/sequel/extensions/columns_introspection.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.

Defined Under Namespace

Modules: ArgumentMapper, NullDataset, Pagination, PreparedStatementMethods, QueryBlockCopy, StoredProcedureMethods, StoredProcedures, UnnumberedArgumentMapper

Constant Summary collapse

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
BOOL_FALSE = 
"'f'".freeze
BOOL_TRUE = 
"'t'".freeze
BRACKET_CLOSE = 
']'.freeze
BRACKET_OPEN = 
'['.freeze
CASE_ELSE = 
" ELSE ".freeze
CASE_END = 
" END)".freeze
CASE_OPEN = 
'(CASE'.freeze
CASE_THEN = 
" THEN ".freeze
CASE_WHEN = 
" WHEN ".freeze
CAST_OPEN = 
'CAST('.freeze
COLUMN_REF_RE1 = 
/\A((?:(?!__).)+)__((?:(?!___).)+)___(.+)\z/.freeze
COLUMN_REF_RE2 = 
/\A((?:(?!___).)+)___(.+)\z/.freeze
COLUMN_REF_RE3 = 
/\A((?:(?!__).)+)__(.+)\z/.freeze
COMMA = 
', '.freeze
COMMA_SEPARATOR = 
COMMA
CONDITION_FALSE = 
'(1 = 0)'.freeze
CONDITION_TRUE = 
'(1 = 1)'.freeze
COUNT_FROM_SELF_OPTS = 
[:distinct, :group, :sql, :limit, :compounds]
COUNT_OF_ALL_AS_COUNT = 
SQL::Function.new(:count, 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
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
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
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
PUBLIC_APPEND_METHODS = 
(<<-END).split.map{|x| x.to_sym}
  literal
  aliased_expression_sql
  array_sql
  boolean_constant_sql
  case_expression_sql
  cast_sql
  column_all_sql
  complex_expression_sql
  constant_sql
  function_sql
  join_clause_sql
  join_on_clause_sql
  join_using_clause_sql
  negative_boolean_constant_sql
  ordered_expression_sql
  placeholder_literal_string_sql
  qualified_identifier_sql
  quote_identifier
  quote_schema_table
  quoted_identifier
  subscript_sql
  window_sql
  window_function_sql
END
PRIVATE_APPEND_METHODS = 
(<<-END).split.map{|x| x.to_sym}
  argument_list
  as_sql
  column_list
  compound_dataset_sql
  expression_list
  literal_array
  literal_blob
  literal_dataset
  literal_expression
  literal_hash
  literal_other
  literal_string
  literal_symbol
  source_list
  subselect_sql
  table_ref
END
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
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 or order order_append order_by order_more order_prepend paginate qualify query
  reverse reverse_order select select_all select_append select_group select_more server
  set_defaults set_graph_aliases set_overrides unfiltered ungraphed ungrouped union
  unlimited unordered where with with_recursive with_sql
METHS
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 get import insert insert_multiple interval last
  map max min multi_insert range select_hash select_hash_groups select_map select_order_map
  set single_record single_value sum to_csv to_hash to_hash_groups truncate update
METHS
MUTATION_METHODS =

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

QUERY_METHODS - [:paginate, :naked]
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 Metaprogramming

meta_def

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

#initialize(db, opts = nil) ⇒ Dataset

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.



28
29
30
31
 
# File 'lib/sequel/dataset/misc.rb', line 28

def initialize(db, opts = nil)
  @db = db
  @opts = opts || {}
end

Instance Attribute Details

#db ⇒ Object

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



15
16
17
 
# File 'lib/sequel/dataset/misc.rb', line 15

def db
  @db
end

#identifier_input_method ⇒ Object

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



115
116
117
118
119
120
121
122
123
 
# File 'lib/sequel/dataset/misc.rb', line 115

def identifier_input_method
  if defined?(@identifier_input_method)
    @identifier_input_method
  elsif db.respond_to?(:identifier_input_method)
    @identifier_input_method = db.identifier_input_method
  else
    @identifier_input_method = nil
  end
end

#identifier_output_method ⇒ Object

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



127
128
129
130
131
132
133
134
135
 
# File 'lib/sequel/dataset/misc.rb', line 127

def identifier_output_method
  if defined?(@identifier_output_method)
    @identifier_output_method
  elsif db.respond_to?(:identifier_output_method)
    @identifier_output_method = db.identifier_output_method
  else
    @identifier_output_method = nil
  end
end

#opts ⇒ Object

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



18
19
20
 
# File 'lib/sequel/dataset/misc.rb', line 18

def opts
  @opts
end

#quote_identifiers=(value) ⇒ Object (writeonly)

Whether to quote identifiers for this dataset



30
31
32
 
# File 'lib/sequel/dataset/mutation.rb', line 30

def quote_identifiers=(value)
  @quote_identifiers = value
end

#row_proc ⇒ Object

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.



34
35
36
 
# File 'lib/sequel/dataset/mutation.rb', line 34

def row_proc
  @row_proc
end

Class Method Details

.clause_methods(type, clauses) ⇒ Object

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



181
182
183
 
# File 'lib/sequel/dataset/sql.rb', line 181

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

.def_append_methods(meths) ⇒ Object 



326
327
328
329
330
331
332
333
334
335
336
 
# File 'lib/sequel/dataset/sql.rb', line 326

def self.def_append_methods(meths)
  meths.each do |meth|
    class_eval(<<-END, __FILE__, __LINE__ + 1)
      def #{meth}(*args, &block)
        s = ''
        #{meth}_append(s, *args, &block)
        s
      end
    END
  end
end

.def_mutation_method(*meths) ⇒ Object

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.



14
15
16
17
18
 
# File 'lib/sequel/dataset/mutation.rb', line 14

def self.def_mutation_method(*meths)
  meths.each do |meth|
    class_eval("def #{meth}!(*args, &block); mutation_method(:#{meth}, *args, &block) end", __FILE__, __LINE__)
  end
end

.introspect_all_columns ⇒ Object

Enable column introspection for every dataset.



56
57
58
59
 
# File 'lib/sequel/extensions/columns_introspection.rb', line 56

def self.introspect_all_columns
  include ColumnsIntrospection
  remove_method(:columns) if instance_methods(false).map{|x| x.to_s}.include?('columns')
end

Instance Method Details

#<<(arg) ⇒ Object

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)



22
23
24
25
 
# File 'lib/sequel/dataset/actions.rb', line 22

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

#==(o) ⇒ Object

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



35
36
37
 
# 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

#[](*conditions) ⇒ Object

Returns the first record matching the conditions. Examples:

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

Raises:



31
32
33
34
 
# 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

#[]=(conditions, values) ⇒ Object

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

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



41
42
43
 
# File 'lib/sequel/dataset/actions.rb', line 41

def []=(conditions, values)
  filter(conditions).update(values)
end

#add_graph_aliases(graph_aliases) ⇒ Object

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

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



17
18
19
20
21
22
 
# File 'lib/sequel/dataset/graph.rb', line 17

def add_graph_aliases(graph_aliases)
  columns, graph_aliases = graph_alias_columns(graph_aliases)
  ds = select_more(*columns)
  ds.opts[:graph_aliases] = (ds.opts[:graph_aliases] || (ds.opts[:graph][:column_aliases] rescue {}) || {}).merge(graph_aliases)
  ds
end

#aliased_expression_sql_append(sql, ae) ⇒ Object

SQL fragment for AliasedExpression



341
342
343
344
 
# File 'lib/sequel/dataset/sql.rb', line 341

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

#all(&block) ⇒ Object

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}



53
54
55
56
57
58
59
 
# File 'lib/sequel/dataset/actions.rb', line 53

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

#and(*cond, &block) ⇒ Object

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

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

Raises:



45
46
47
48
 
# File 'lib/sequel/dataset/query.rb', line 45

def and(*cond, &block)
  raise(InvalidOperation, "No existing filter found.") unless @opts[:having] || @opts[:where]
  filter(*cond, &block)
end

#array_sql_append(sql, a) ⇒ Object

SQL fragment for Array



347
348
349
350
351
352
353
354
355
 
# File 'lib/sequel/dataset/sql.rb', line 347

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

#avg(column) ⇒ Object

Returns the average value for the given column.

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



65
66
67
 
# File 'lib/sequel/dataset/actions.rb', line 65

def avg(column)
  aggregate_dataset.get{avg(column)}
end

#bind(bind_vars = {}) ⇒ Object

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}



215
216
217
 
# File 'lib/sequel/dataset/prepared_statements.rb', line 215

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

#boolean_constant_sql_append(sql, constant) ⇒ Object

SQL fragment for BooleanConstants



358
359
360
361
362
363
364
 
# File 'lib/sequel/dataset/sql.rb', line 358

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

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

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}



226
227
228
 
# File 'lib/sequel/dataset/prepared_statements.rb', line 226

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

#case_expression_sql_append(sql, ce) ⇒ Object

SQL fragment for CaseExpression



367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
 
# File 'lib/sequel/dataset/sql.rb', line 367

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

#cast_sql_append(sql, expr, type) ⇒ Object

SQL fragment for the SQL CAST expression



387
388
389
390
391
392
 
# File 'lib/sequel/dataset/sql.rb', line 387

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

#clone(opts = {}) ⇒ Object

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.



54
55
56
57
58
59
 
# File 'lib/sequel/dataset/query.rb', line 54

def clone(opts = {})
  c = super()
  c.opts = @opts.merge(opts)
  c.instance_variable_set(:@columns, nil) if opts.keys.any?{|o| COLUMN_CHANGE_OPTS.include?(o)}
  c
end

#column_all_sql_append(sql, ca) ⇒ Object

SQL fragment for specifying all columns in a given table



395
396
397
 
# File 'lib/sequel/dataset/sql.rb', line 395

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

#columns ⇒ Object Also known as: columns_without_introspection

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]



78
79
80
81
82
83
84
 
# File 'lib/sequel/dataset/actions.rb', line 78

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

#columns! ⇒ Object

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

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



91
92
93
94
 
# File 'lib/sequel/dataset/actions.rb', line 91

def columns!
  @columns = nil
  columns
end

#complex_expression_sql_append(sql, op, args) ⇒ Object

SQL fragment for the complex expression.



400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
 
# File 'lib/sequel/dataset/sql.rb', line 400

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 v = IS_LITERALS[r]
      sql << PAREN_OPEN
      literal_append(sql, args.at(0))
      sql << SPACE << op.to_s << SPACE
      sql << v << 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 *TWO_ARITY_OPERATORS
    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

#constant_sql_append(sql, constant) ⇒ Object

SQL fragment for constants



492
493
494
 
# File 'lib/sequel/dataset/sql.rb', line 492

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

#count ⇒ Object

Returns the number of records in the dataset.

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



100
101
102
 
# File 'lib/sequel/dataset/actions.rb', line 100

def count
  aggregate_dataset.get{COUNT(:*){}.as(count)}.to_i
end

#def_mutation_method(*meths) ⇒ Object

Add a mutation method to this dataset instance.



37
38
39
40
41
 
# File 'lib/sequel/dataset/mutation.rb', line 37

def def_mutation_method(*meths)
  meths.each do |meth|
    instance_eval("def #{meth}!(*args, &block); mutation_method(:#{meth}, *args, &block) end", __FILE__, __LINE__)
  end
end

#delete(&block) ⇒ Object

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



109
110
111
112
113
114
115
116
 
# File 'lib/sequel/dataset/actions.rb', line 109

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

#delete_sql ⇒ Object

Returns a DELETE SQL query string. See delete.

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



12
13
14
15
16
 
# 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

#distinct(*args) ⇒ Object

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:



70
71
72
73
 
# File 'lib/sequel/dataset/query.rb', line 70

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

#each ⇒ Object

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:



127
128
129
130
131
132
133
134
135
136
 
# File 'lib/sequel/dataset/actions.rb', line 127

def each
  if @opts[:graph]
    graph_each{|r| yield r}
  elsif 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

#each_page(page_size) ⇒ Object

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

Raises:



20
21
22
23
24
25
26
 
# File 'lib/sequel/extensions/pagination.rb', line 20

def each_page(page_size)
  raise(Error, "You cannot paginate a dataset that already has a limit") if @opts[:limit]
  record_count = count
  total_pages = (record_count / page_size.to_f).ceil
  (1..total_pages).each{|page_no| yield paginate(page_no, page_size, record_count)}
  self
end

#each_server ⇒ Object

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')}



49
50
51
 
# File 'lib/sequel/dataset/misc.rb', line 49

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

#empty? ⇒ Boolean

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) 


142
143
144
 
# File 'lib/sequel/dataset/actions.rb', line 142

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

#eql?(o) ⇒ Boolean

Alias for ==

Returns:

  • (Boolean) 


40
41
42
 
# File 'lib/sequel/dataset/misc.rb', line 40

def eql?(o)
  self == o
end

#except(dataset, opts = {}) ⇒ Object

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:



92
93
94
95
96
97
 
# File 'lib/sequel/dataset/query.rb', line 92

def except(dataset, opts={})
  opts = {:all=>opts} unless opts.is_a?(Hash)
  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

#exclude(*cond, &block) ⇒ Object

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

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

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



107
108
109
 
# File 'lib/sequel/dataset/query.rb', line 107

def exclude(*cond, &block)
  _filter_or_exclude(true, @opts[:having] ? :having : :where, *cond, &block)
end

#exclude_having(*cond, &block) ⇒ Object

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)



115
116
117
 
# File 'lib/sequel/dataset/query.rb', line 115

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

#exclude_where(*cond, &block) ⇒ Object

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

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

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



129
130
131
 
# File 'lib/sequel/dataset/query.rb', line 129

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

#exists ⇒ Object

Returns an EXISTS clause for the dataset as a LiteralString.

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



22
23
24
 
# File 'lib/sequel/dataset/sql.rb', line 22

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

#fetch_rows(sql) ⇒ Object

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

Raises:



150
151
152
 
# File 'lib/sequel/dataset/actions.rb', line 150

def fetch_rows(sql)
  raise NotImplemented, NOTIMPL_MSG
end

#filter(*cond, &block) ⇒ Object

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

If the query already has a HAVING clause, then the conditions are imposed in the HAVING clause. If not, then they are imposed in the WHERE clause.

filter accepts the following argument types:

  • Hash - list of equality/inclusion expressions

  • Array - depends:

    • If first member is a string, assumes the rest of the arguments are parameters and interpolates them into the string.

    • If all members are arrays of length two, treats the same way as a hash, except it allows for duplicate keys to be specified.

    • Otherwise, treats each argument as a separate condition.

  • String - taken literally

  • Symbol - taken as a boolean column argument (e.g. WHERE active)

  • Sequel::SQL::BooleanExpression - an existing condition expression, probably created using the Sequel expression filter DSL.

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

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

Examples:

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

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

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

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

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

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

Multiple filter calls can be chained for scoping:

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

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



185
186
187
 
# File 'lib/sequel/dataset/query.rb', line 185

def filter(*cond, &block)
  _filter(@opts[:having] ? :having : :where, *cond, &block)
end

#first(*args, &block) ⇒ Object

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

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

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

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

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

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

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

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

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



184
185
186
187
188
189
190
191
192
193
194
195
196
197
 
# File 'lib/sequel/dataset/actions.rb', line 184

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

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

#first_source ⇒ Object

Alias of first_source_alias



54
55
56
 
# File 'lib/sequel/dataset/misc.rb', line 54

def first_source
  first_source_alias
end

#first_source_alias ⇒ Object

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



66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
 
# File 'lib/sequel/dataset/misc.rb', line 66

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.aliaz
  when Symbol
    sch, table, aliaz = split_symbol(s)
    aliaz ? aliaz.to_sym : s
  else
    s
  end
end

#first_source_table ⇒ Object

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



91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
 
# File 'lib/sequel/dataset/misc.rb', line 91

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

#for_update ⇒ Object

Returns a cloned dataset with a :update lock style.

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



192
193
194
 
# File 'lib/sequel/dataset/query.rb', line 192

def for_update
  lock_style(:update)
end

#from(*source) ⇒ Object

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

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



203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
 
# File 'lib/sequel/dataset/query.rb', line 203

def from(*source)
  table_alias_num = 0
  sources = []
  ctes = nil
  source.each do |s|
    case s
    when Hash
      s.each{|k,v| sources << SQL::AliasedExpression.new(k,v)}
    when Dataset
      if hoist_cte?(s)
        ctes ||= []
        ctes += s.opts[:with]
        s = s.clone(:with=>nil)
      end
      sources << 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)
        sources << SQL::AliasedExpression.new(s, aliaz.to_sym)
      else
        sources << s
      end
    else
      sources << s
    end
  end
  o = {:from=>sources.empty? ? nil : sources}
  o[:with] = (opts[:with] || []) + ctes if ctes
  o[:num_dataset_sources] = table_alias_num if table_alias_num > 0
  clone(o)
end

#from_self(opts = {}) ⇒ Object

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



247
248
249
250
251
 
# File 'lib/sequel/dataset/query.rb', line 247

def from_self(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

#function_sql_append(sql, f) ⇒ Object

SQL fragment specifying an SQL function call



497
498
499
500
501
502
503
504
505
 
# File 'lib/sequel/dataset/sql.rb', line 497

def function_sql_append(sql, f)
  sql << f.f.to_s
  args = f.args
  if args.empty?
    sql << FUNCTION_EMPTY
  else
    literal_append(sql, args)
  end
end

#get(column = nil, &block) ⇒ Object

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

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

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



207
208
209
210
211
212
213
214
 
# File 'lib/sequel/dataset/actions.rb', line 207

def get(column=nil, &block)
  if column
    raise(Error, ARG_BLOCK_ERROR_MSG) if block
    select(column).single_value
  else
    select(&block).single_value
  end
end

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

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

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

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

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

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

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

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

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

Arguments:

dataset

Can be a symbol (specifying a table), another dataset, or an object that responds to dataset and returns a symbol or a dataset

join_conditions

Any condition(s) allowed by join_table.

block

A block that is passed to join_table.

Options:

:from_self_alias

The alias to use when the receiver is not a graphed dataset but it contains multiple FROM tables or a JOIN. In this case, the receiver is wrapped in a from_self before graphing, and this option determines the alias to use.

:implicit_qualifier

The qualifier of implicit conditions, see #join_table.

:join_type

The type of join to use (passed to join_table). Defaults to :left_outer.

:select

An array of columns to select. When not used, selects all columns in the given dataset. When set to false, selects no columns and is like simply joining the tables, though graph keeps some metadata about the join that makes it important to use graph instead of join_table.

:table_alias

The alias to use for the table. If not specified, doesn’t alias the table. You will get an error if the the alias (or table) name is used more than once.



74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
 
# File 'lib/sequel/dataset/graph.rb', line 74

def graph(dataset, join_conditions = nil, options = {}, &block)
  # Allow the use of a model, dataset, or symbol as the first argument
  # Find the table name/dataset based on the argument
  dataset = dataset.dataset if dataset.respond_to?(:dataset)
  table_alias = options[:table_alias]
  case dataset
  when Symbol
    table = dataset
    dataset = @db[dataset]
    table_alias ||= table
  when ::Sequel::Dataset
    if dataset.simple_select_all?
      table = dataset.opts[:from].first
      table_alias ||= table
    else
      table = dataset
      table_alias ||= dataset_alias((@opts[:num_dataset_sources] || 0)+1)
    end
  else
    raise Error, "The dataset argument should be a symbol, dataset, or model"
  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)
  
  # Use a from_self if this is already a joined table
  ds = (!@opts[:graph] && (@opts[:from].length > 1 || @opts[:join])) ? from_self(:alias=>options[:from_self_alias] || first_source) : self
  
  # 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, :implicit_qualifier=>options[:implicit_qualifier], &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
    master = alias_symbol(ds.first_source_alias)
    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.aliaz
            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, master)
      else
        select = columns.map do |column|
          column_aliases[column] = [master, column]
          SQL::QualifiedIdentifier.new(master, 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, column), column_alias)]
      else
        ident = SQL::QualifiedIdentifier.new(table_alias, column)
        [column, ident]
      end
      column_aliases[col_alias] = [table_alias, column]
      select.push(identifier)
    end
  end
  add_columns ? ds.select(*select) : ds
end

#grep(columns, patterns, opts = {}) ⇒ Object

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%'))



284
285
286
287
288
289
290
291
292
293
294
295
296
 
# File 'lib/sequel/dataset/query.rb', line 284

def grep(columns, patterns, 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
    filter(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
    filter(SQL::BooleanExpression.new(opts[:all_columns] ? :AND : :OR, *conds))
  end
end

#group(*columns, &block) ⇒ Object

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

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



305
306
307
308
 
# File 'lib/sequel/dataset/query.rb', line 305

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

#group_and_count(*columns, &block) ⇒ Object

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

Examples:

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

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

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

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



336
337
338
 
# File 'lib/sequel/dataset/query.rb', line 336

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

#group_by(*columns, &block) ⇒ Object

Alias of group



311
312
313
 
# File 'lib/sequel/dataset/query.rb', line 311

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

#group_cube ⇒ Object

Adds the appropriate CUBE syntax to GROUP BY.

Raises:



341
342
343
344
 
# File 'lib/sequel/dataset/query.rb', line 341

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

#group_rollup ⇒ Object

Adds the appropriate ROLLUP syntax to GROUP BY.

Raises:



347
348
349
350
 
# File 'lib/sequel/dataset/query.rb', line 347

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

#hash ⇒ Object

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



109
110
111
 
# File 'lib/sequel/dataset/misc.rb', line 109

def hash
  [db, opts.sort_by{|k, v| k.to_s}, sql].hash
end

#having(*cond, &block) ⇒ Object

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

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



356
357
358
 
# File 'lib/sequel/dataset/query.rb', line 356

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

#import(columns, values, opts = {}) ⇒ Object

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

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

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

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

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

Options:

:commit_every

Open a new transaction for every given number of records. For example, if you provide a value of 50, will commit after every 50 records.

:server

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

:slice

Same as :commit_every, :commit_every takes precedence.

Raises:



239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
 
# File 'lib/sequel/dataset/actions.rb', line 239

def import(columns, values, 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

#insert(*values, &block) ⇒ Object

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



294
295
296
297
298
299
300
301
 
# File 'lib/sequel/dataset/actions.rb', line 294

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

#insert_multiple(array, &block) ⇒ Object

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

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

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



318
319
320
321
322
323
324
 
# File 'lib/sequel/dataset/actions.rb', line 318

def insert_multiple(array, &block)
  if block
    array.map{|i| insert(block.call(i))}
  else
    array.map{|i| insert(i)}
  end
end

#insert_sql(*values) ⇒ Object

Returns an INSERT SQL query string. See insert.

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



30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
 
# 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
      vals = @opts[:defaults].merge(vals) if @opts[:defaults]
      vals = vals.merge(@opts[:overrides]) if @opts[:overrides]
      values = []
      vals.each do |k,v| 
        columns << k
        values << v
      end
    when Dataset, Array, LiteralString
      values = vals
    else
      if vals.respond_to?(:values) && (v = vals.values).is_a?(Hash)
        return insert_sql(v) 
      end
    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

#inspect ⇒ Object

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



139
140
141
142
143
 
# File 'lib/sequel/dataset/misc.rb', line 139

def inspect
  c = self.class
  c = c.superclass while c.name.nil? || c.name == ''
  "#<#{c.name}: #{sql.inspect}>"
end

#intersect(dataset, opts = {}) ⇒ Object

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:



377
378
379
380
381
382
 
# File 'lib/sequel/dataset/query.rb', line 377

def intersect(dataset, opts={})
  opts = {:all=>opts} unless opts.is_a?(Hash)
  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

#interval(column) ⇒ Object

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

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



331
332
333
 
# File 'lib/sequel/dataset/actions.rb', line 331

def interval(column)
  aggregate_dataset.get{max(column) - min(column)}
end

#invert ⇒ Object

Inverts the current filter.

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

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

Raises:



391
392
393
394
395
396
397
398
 
# File 'lib/sequel/dataset/query.rb', line 391

def invert
  having, where = @opts[:having], @opts[:where]
  raise(Error, "No current filter") unless having || where
  o = {}
  o[:having] = SQL::BooleanExpression.invert(having) if having
  o[:where] = SQL::BooleanExpression.invert(where) if where
  clone(o)
end

#join(*args, &block) ⇒ Object

Alias of inner_join



401
402
403
 
# File 'lib/sequel/dataset/query.rb', line 401

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

#join_clause_sql_append(sql, jc) ⇒ Object

SQL fragment specifying a JOIN clause without ON or USING.



508
509
510
511
512
513
514
515
 
# File 'lib/sequel/dataset/sql.rb', line 508

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

#join_on_clause_sql_append(sql, jc) ⇒ Object

SQL fragment specifying a JOIN clause with ON.



518
519
520
521
522
 
# File 'lib/sequel/dataset/sql.rb', line 518

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

#join_table(type, table, expr = nil, options = {}, &block) ⇒ Object

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

Takes the following arguments:

  • type - The type of join to do (e.g. :inner)

  • table - Depends on type:

    • Dataset - a subselect is performed with an alias of tN for some value of N

    • Model (or anything responding to :table_name) - table.table_name

    • String, Symbol: table

  • expr - specifies conditions, depends on type:

    • Hash, Array of two element arrays - Assumes key (1st arg) is column of joined table (unless already qualified), and value (2nd arg) is column of the last joined or primary table (or the :implicit_qualifier option). To specify multiple conditions on a single joined table column, you must use an array. Uses a JOIN with an ON clause.

    • Array - If all members of the array are symbols, considers them as columns and uses a JOIN with a USING clause. Most databases will remove duplicate columns from the result set if this is used.

    • nil - If a block is not given, doesn’t use ON or USING, so the JOIN should be a NATURAL or CROSS join. If a block is given, uses an ON clause based on the block, see below.

    • Everything else - pretty much the same as a using the argument in a call to filter, so strings are considered literal, symbols specify boolean columns, and Sequel expressions can be used. Uses a JOIN with an ON clause.

  • options - a hash of options, with any of the following keys:

    • :table_alias - the name of the table’s alias when joining, necessary for joining to the same table more than once. No alias is used by default.

    • :implicit_qualifier - The name to use for qualifying implicit conditions. By default, the last joined or primary table is used.

  • block - The block argument should only be given if a JOIN with an ON clause is used, in which case it yields the table alias/name for the table currently being joined, the table alias/name for the last joined (or first table), and an array of previous SQL::JoinClause. Unlike filter, this block is not treated as a virtual row block.

Examples:

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

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

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

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



456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
 
# File 'lib/sequel/dataset/query.rb', line 456

def join_table(type, table, expr=nil, options={}, &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{|s| h[s] = s}
    return join_table(type, table, h, options)
  end

  case options
  when Hash
    table_alias = options[:table_alias]
    last_alias = options[:implicit_qualifier]
  when Symbol, String, SQL::Identifier
    table_alias = options
    last_alias = nil 
  else
    raise Error, "invalid options format for join_table: #{options.inspect}"
  end

  if Dataset === table
    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 = table.table_name if table.respond_to?(:table_name)
    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|
        k = qualified_column_name(k, table_name) if k.is_a?(Symbol)
        v = qualified_column_name(v, last_alias) if v.is_a?(Symbol)
        [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

#join_using_clause_sql_append(sql, jc) ⇒ Object

SQL fragment specifying a JOIN clause with USING.



525
526
527
528
529
530
 
# File 'lib/sequel/dataset/sql.rb', line 525

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

#last(*args, &block) ⇒ Object

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

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

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

Raises:



345
346
347
348
 
# File 'lib/sequel/dataset/actions.rb', line 345

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

#limit(l, o = nil) ⇒ Object

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



537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
 
# File 'lib/sequel/dataset/query.rb', line 537

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

  if Range === l
    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
  opts = {:limit => l}
  if 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
    opts[:offset] = o
  end
  clone(opts)
end

#literal_append(sql, v) ⇒ Object

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.



81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
 
# File 'lib/sequel/dataset/sql.rb', line 81

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

#lock_style(style) ⇒ Object

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

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



565
566
567
 
# File 'lib/sequel/dataset/query.rb', line 565

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

#map(column = nil, &block) ⇒ Object

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'], ...]



364
365
366
367
368
369
370
371
372
373
374
375
376
 
# File 'lib/sequel/dataset/actions.rb', line 364

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

#max(column) ⇒ Object

Returns the maximum value for the given column.

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



382
383
384
 
# File 'lib/sequel/dataset/actions.rb', line 382

def max(column)
  aggregate_dataset.get{max(column)}
end

#min(column) ⇒ Object

Returns the minimum value for the given column.

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



390
391
392
 
# File 'lib/sequel/dataset/actions.rb', line 390

def min(column)
  aggregate_dataset.get{min(column)}
end

#multi_insert(hashes, opts = {}) ⇒ Object

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.



406
407
408
409
410
 
# File 'lib/sequel/dataset/actions.rb', line 406

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

#multi_insert_sql(columns, values) ⇒ Object

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.



131
132
133
 
# File 'lib/sequel/dataset/sql.rb', line 131

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

#naked ⇒ Object

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}]



575
576
577
578
579
 
# File 'lib/sequel/dataset/query.rb', line 575

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

#naked! ⇒ Object

Remove the row_proc from the current dataset.



44
45
46
47
 
# File 'lib/sequel/dataset/mutation.rb', line 44

def naked!
  self.row_proc = nil
  self
end

#negative_boolean_constant_sql_append(sql, constant) ⇒ Object

SQL fragment for NegativeBooleanConstants



533
534
535
536
 
# File 'lib/sequel/dataset/sql.rb', line 533

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

#nullify ⇒ Object

Return a cloned nullified dataset.



81
82
83
 
# File 'lib/sequel/extensions/null_dataset.rb', line 81

def nullify
  clone.nullify!
end

#nullify! ⇒ Object

Nullify the current dataset



86
87
88
 
# File 'lib/sequel/extensions/null_dataset.rb', line 86

def nullify!
  extend NullDataset
end

#or(*cond, &block) ⇒ Object

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

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

Raises:



585
586
587
588
589
590
 
# File 'lib/sequel/dataset/query.rb', line 585

def or(*cond, &block)
  clause = (@opts[:having] ? :having : :where)
  raise(InvalidOperation, "No existing filter found.") unless @opts[clause]
  cond = cond.first if cond.size == 1
  clone(clause => SQL::BooleanExpression.new(:OR, @opts[clause], filter_expr(cond, &block)))
end

#order(*columns, &block) ⇒ Object

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

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



606
607
608
609
 
# File 'lib/sequel/dataset/query.rb', line 606

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

#order_append(*columns, &block) ⇒ Object

Alias of order_more, for naming consistency with order_prepend.



612
613
614
 
# File 'lib/sequel/dataset/query.rb', line 612

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

#order_by(*columns, &block) ⇒ Object

Alias of order



617
618
619
 
# File 'lib/sequel/dataset/query.rb', line 617

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

#order_more(*columns, &block) ⇒ Object

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



626
627
628
629
 
# File 'lib/sequel/dataset/query.rb', line 626

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

#order_prepend(*columns, &block) ⇒ Object

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



636
637
638
639
 
# File 'lib/sequel/dataset/query.rb', line 636

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

#ordered_expression_sql_append(sql, oe) ⇒ Object

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



540
541
542
543
544
545
546
547
548
549
 
# File 'lib/sequel/dataset/sql.rb', line 540

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

#paginate(page_no, page_size, record_count = nil) ⇒ Object

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

Raises:



11
12
13
14
15
16
 
# File 'lib/sequel/extensions/pagination.rb', line 11

def paginate(page_no, page_size, record_count=nil)
  raise(Error, "You cannot paginate a dataset that already has a limit") if @opts[:limit]
  paginated = limit(page_size, (page_no - 1) * page_size)
  paginated.extend(Pagination)
  paginated.set_pagination_info(page_no, page_size, record_count || count)
end

#placeholder_literal_string_sql_append(sql, pls) ⇒ Object

SQL fragment for a literal string with placeholders



552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
 
# File 'lib/sequel/dataset/sql.rb', line 552

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)
    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
  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
  else
    i = -1
    loop do
      previous, q, str = str.partition(QUESTION_MARK)
      sql << previous
       literal_append(sql, args.at(i+=1)) unless q.empty?
      break if str.empty?
    end
  end
  sql << PAREN_CLOSE if pls.parens
end

#prepare(type, name = nil, *values) ⇒ Object

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



248
249
250
251
252
 
# File 'lib/sequel/dataset/prepared_statements.rb', line 248

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

#print(*cols) ⇒ Object

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



10
11
12
13
14
 
# File 'lib/sequel/extensions/pretty_table.rb', line 10

def print(*cols)
  ds = naked
  rows = ds.all
  Sequel::PrettyTable.print(rows, cols.empty? ? ds.columns : cols)
end

#provides_accurate_rows_matched? ⇒ Boolean

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) 


23
24
25
 
# File 'lib/sequel/dataset/features.rb', line 23

def provides_accurate_rows_matched?
  true
end

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

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.



586
587
588
589
590
 
# File 'lib/sequel/dataset/sql.rb', line 586

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

#qualify(table = first_source) ⇒ Object

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

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

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



648
649
650
 
# File 'lib/sequel/dataset/query.rb', line 648

def qualify(table=first_source)
  qualify_to(table)
end

#qualify_to(table) ⇒ Object

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

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



659
660
661
662
663
664
665
666
667
668
 
# File 'lib/sequel/dataset/query.rb', line 659

def qualify_to(table)
  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

#qualify_to_first_source ⇒ Object

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

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



678
679
680
 
# File 'lib/sequel/dataset/query.rb', line 678

def qualify_to_first_source
  qualify_to(first_source)
end

#query(&block) ⇒ Object

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

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

Which is the same as:

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

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



30
31
32
33
34
35
 
# File 'lib/sequel/extensions/query.rb', line 30

def query(&block)
  copy = clone({})
  copy.extend(QueryBlockCopy)
  copy.instance_eval(&block)
  clone(copy.opts)
end

#quote_identifier_append(sql, name) ⇒ Object

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.



595
596
597
598
599
600
601
602
603
604
605
606
607
 
# File 'lib/sequel/dataset/sql.rb', line 595

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

#quote_identifiers? ⇒ Boolean

Whether this dataset quotes identifiers.

Returns:

  • (Boolean) 


10
11
12
13
14
15
16
17
18
 
# File 'lib/sequel/dataset/features.rb', line 10

def quote_identifiers?
  if defined?(@quote_identifiers)
    @quote_identifiers
  elsif db.respond_to?(:quote_identifiers?)
    @quote_identifiers = db.quote_identifiers?
  else
    @quote_identifiers = false
  end
end

#quote_schema_table_append(sql, table) ⇒ Object

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



611
612
613
614
615
616
617
618
 
# File 'lib/sequel/dataset/sql.rb', line 611

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

#quoted_identifier_append(sql, name) ⇒ Object

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).



623
624
625
 
# File 'lib/sequel/dataset/sql.rb', line 623

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

#range(column) ⇒ Object

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

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



417
418
419
420
421
 
# File 'lib/sequel/dataset/actions.rb', line 417

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

#recursive_cte_requires_column_aliases? ⇒ Boolean

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

Returns:

  • (Boolean) 


29
30
31
 
# File 'lib/sequel/dataset/features.rb', line 29

def recursive_cte_requires_column_aliases?
  false
end

#requires_placeholder_type_specifiers? ⇒ Boolean

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

Returns:

  • (Boolean) 


41
42
43
 
# File 'lib/sequel/dataset/features.rb', line 41

def requires_placeholder_type_specifiers?
  false
end

#requires_sql_standard_datetimes? ⇒ Boolean

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

Returns:

  • (Boolean) 


35
36
37
 
# File 'lib/sequel/dataset/features.rb', line 35

def requires_sql_standard_datetimes?
  false
end

#returning(*values) ⇒ Object

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



690
691
692
 
# File 'lib/sequel/dataset/query.rb', line 690

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

#reverse(*order) ⇒ Object

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

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



700
701
702
 
# File 'lib/sequel/dataset/query.rb', line 700

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

#reverse_order(*order) ⇒ Object

Alias of reverse



705
706
707
 
# File 'lib/sequel/dataset/query.rb', line 705

def reverse_order(*order)
  reverse(*order)
end

#row_number_column ⇒ Object

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



147
148
149
 
# File 'lib/sequel/dataset/misc.rb', line 147

def row_number_column
  :x_sequel_row_number_x
end

#schema_and_table(table_name) ⇒ Object

Split the schema information from the table



628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
 
# File 'lib/sequel/dataset/sql.rb', line 628

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

#select(*columns, &block) ⇒ Object

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

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



716
717
718
719
720
721
722
723
 
# File 'lib/sequel/dataset/query.rb', line 716

def select(*columns, &block)
  virtual_row_columns(columns, block)
  m = []
  columns.each do |i|
    i.is_a?(Hash) ? m.concat(i.map{|k, v| SQL::AliasedExpression.new(k,v)}) : m << i
  end
  clone(:select => m)
end

#select_all(*tables) ⇒ Object

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



732
733
734
735
736
737
738
 
# File 'lib/sequel/dataset/query.rb', line 732

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

#select_append(*columns, &block) ⇒ Object

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



747
748
749
750
751
752
753
754
755
756
 
# File 'lib/sequel/dataset/query.rb', line 747

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

#select_group(*columns, &block) ⇒ Object

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

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

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



767
768
769
770
 
# File 'lib/sequel/dataset/query.rb', line 767

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

#select_hash(key_column, value_column) ⇒ Object

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.



438
439
440
 
# File 'lib/sequel/dataset/actions.rb', line 438

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

#select_hash_groups(key_column, value_column) ⇒ Object

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.



457
458
459
 
# File 'lib/sequel/dataset/actions.rb', line 457

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

#select_map(column = nil, &block) ⇒ Object

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.



481
482
483
 
# File 'lib/sequel/dataset/actions.rb', line 481

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

#select_more(*columns, &block) ⇒ Object

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

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



779
780
781
782
 
# File 'lib/sequel/dataset/query.rb', line 779

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

#select_order_map(column = nil, &block) ⇒ Object

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.



501
502
503
 
# File 'lib/sequel/dataset/actions.rb', line 501

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

#select_remove(*cols) ⇒ Object

Remove columns from the list of selected columns. If any of the currently selected columns use expressions/aliases, this will remove selected columns with the given aliases. It will also remove entries from the selection that match exactly:

# Assume columns a, b, and c in items table
DB[:items] # SELECT * FROM items
DB[:items].select_remove(:c) # SELECT a, b FROM items
DB[:items].select(:a, :b___c, :c___b).select_remove(:c) # SELECT a, c AS b FROM items
DB[:items].select(:a, :b___c, :c___b).select_remove(:c___b) # SELECT a, b AS c FROM items

Note that there are a few cases where this method may not work correctly:

  • This dataset joins multiple tables and does not have an existing explicit selection. In this case, the code will currently use unqualified column names for all columns the dataset returns, except for the columns given.

  • This dataset has an existing explicit selection containing an item that returns multiple database columns (e.g. :table.*, ‘column1, column2’.lit). In this case, the behavior is undefined and this method should not be used.

There may be other cases where this method does not work correctly, use it with caution.



27
28
29
30
31
32
33
 
# File 'lib/sequel/extensions/select_remove.rb', line 27

def select_remove(*cols)
  if (sel = @opts[:select]) && !sel.empty?
    select(*(columns.zip(sel).reject{|c, s| cols.include?(c)}.map{|c, s| s} - cols))
  else
    select(*(columns - cols))
  end
end

#select_sql ⇒ Object

Returns a SELECT SQL query string.

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



138
139
140
141
 
# File 'lib/sequel/dataset/sql.rb', line 138

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

#server(servr) ⇒ Object

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



793
794
795
 
# File 'lib/sequel/dataset/query.rb', line 793

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

#set(*args) ⇒ Object

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



507
508
509
 
# File 'lib/sequel/dataset/actions.rb', line 507

def set(*args)
  update(*args)
end

#set_defaults(hash) ⇒ Object

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

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



803
804
805
 
# File 'lib/sequel/dataset/query.rb', line 803

def set_defaults(hash)
  clone(:defaults=>(@opts[:defaults]||{}).merge(hash))
end

#set_graph_aliases(graph_aliases) ⇒ Object

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

graph_aliases

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

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



230
231
232
233
234
235
 
# File 'lib/sequel/dataset/graph.rb', line 230

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

#set_overrides(hash) ⇒ Object

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

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



813
814
815
 
# File 'lib/sequel/dataset/query.rb', line 813

def set_overrides(hash)
  clone(:overrides=>hash.merge(@opts[:overrides]||{}))
end

#single_record ⇒ Object

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



514
515
516
517
 
# File 'lib/sequel/dataset/actions.rb', line 514

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

#single_value ⇒ Object

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.



522
523
524
525
526
 
# File 'lib/sequel/dataset/actions.rb', line 522

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

#split_alias(c) ⇒ Object

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.



154
155
156
157
158
159
160
161
162
163
164
165
166
 
# File 'lib/sequel/dataset/misc.rb', line 154

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.aliaz]
  when SQL::JoinClause
    [c.table, c.table_alias]
  else
    [c, nil]
  end
end

#sql ⇒ Object

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



144
145
146
 
# File 'lib/sequel/dataset/sql.rb', line 144

def sql
  select_sql
end

#subscript_sql_append(sql, s) ⇒ Object

SQL fragment for specifying subscripts (SQL array accesses)



646
647
648
649
650
651
 
# File 'lib/sequel/dataset/sql.rb', line 646

def subscript_sql_append(sql, s)
  literal_append(sql, s.f)
  sql << BRACKET_OPEN
  expression_list_append(sql, s.sub)
  sql << BRACKET_CLOSE
end

#sum(column) ⇒ Object

Returns the sum for the given column.

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



532
533
534
 
# File 'lib/sequel/dataset/actions.rb', line 532

def sum(column)
  aggregate_dataset.get{sum(column)}
end

#supports_cte?(type = :select) ⇒ Boolean

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) 


48
49
50
 
# File 'lib/sequel/dataset/features.rb', line 48

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

#supports_cte_in_subqueries? ⇒ Boolean

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) 


55
56
57
 
# File 'lib/sequel/dataset/features.rb', line 55

def supports_cte_in_subqueries?
  false
end

#supports_distinct_on? ⇒ Boolean

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

Returns:

  • (Boolean) 


60
61
62
 
# File 'lib/sequel/dataset/features.rb', line 60

def supports_distinct_on?
  false
end

#supports_group_cube? ⇒ Boolean

Whether the dataset supports CUBE with GROUP BY.

Returns:

  • (Boolean) 


65
66
67
 
# File 'lib/sequel/dataset/features.rb', line 65

def supports_group_cube?
  false
end

#supports_group_rollup? ⇒ Boolean

Whether the dataset supports ROLLUP with GROUP BY.

Returns:

  • (Boolean) 


70
71
72
 
# File 'lib/sequel/dataset/features.rb', line 70

def supports_group_rollup?
  false
end

#supports_insert_select? ⇒ Boolean

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

Returns:

  • (Boolean) 


76
77
78
 
# File 'lib/sequel/dataset/features.rb', line 76

def supports_insert_select?
  supports_returning?(:insert)
end

#supports_intersect_except? ⇒ Boolean

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

Returns:

  • (Boolean) 


81
82
83
 
# File 'lib/sequel/dataset/features.rb', line 81

def supports_intersect_except?
  true
end

#supports_intersect_except_all? ⇒ Boolean

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

Returns:

  • (Boolean) 


86
87
88
 
# File 'lib/sequel/dataset/features.rb', line 86

def supports_intersect_except_all?
  true
end

#supports_is_true? ⇒ Boolean

Whether the dataset supports the IS TRUE syntax.

Returns:

  • (Boolean) 


91
92
93
 
# File 'lib/sequel/dataset/features.rb', line 91

def supports_is_true?
  true
end

#supports_join_using? ⇒ Boolean

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

Returns:

  • (Boolean) 


96
97
98
 
# File 'lib/sequel/dataset/features.rb', line 96

def supports_join_using?
  true
end

#supports_modifying_joins? ⇒ Boolean

Whether modifying joined datasets is supported.

Returns:

  • (Boolean) 


101
102
103
 
# File 'lib/sequel/dataset/features.rb', line 101

def supports_modifying_joins?
  false
end

#supports_multiple_column_in? ⇒ Boolean

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

Returns:

  • (Boolean) 


107
108
109
 
# File 'lib/sequel/dataset/features.rb', line 107

def supports_multiple_column_in?
  true
end

#supports_ordered_distinct_on? ⇒ Boolean

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

Returns:

  • (Boolean) 


113
114
115
 
# File 'lib/sequel/dataset/features.rb', line 113

def supports_ordered_distinct_on?
  supports_distinct_on?
end

#supports_returning?(type) ⇒ Boolean

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

Returns:

  • (Boolean) 


119
120
121
 
# File 'lib/sequel/dataset/features.rb', line 119

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

#supports_select_all_and_column? ⇒ Boolean

Whether the database supports SELECT *, column FROM table

Returns:

  • (Boolean) 


124
125
126
 
# File 'lib/sequel/dataset/features.rb', line 124

def supports_select_all_and_column?
  true
end

#supports_timestamp_timezones? ⇒ Boolean

Whether the dataset supports timezones in literal timestamps

Returns:

  • (Boolean) 


129
130
131
 
# File 'lib/sequel/dataset/features.rb', line 129

def supports_timestamp_timezones?
  false
end

#supports_timestamp_usecs? ⇒ Boolean

Whether the dataset supports fractional seconds in literal timestamps

Returns:

  • (Boolean) 


134
135
136
 
# File 'lib/sequel/dataset/features.rb', line 134

def supports_timestamp_usecs?
  true
end

#supports_where_true? ⇒ Boolean

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

Returns:

  • (Boolean) 


145
146
147
 
# File 'lib/sequel/dataset/features.rb', line 145

def supports_where_true?
  true
end

#supports_window_functions? ⇒ Boolean

Whether the dataset supports window functions.

Returns:

  • (Boolean) 


139
140
141
 
# File 'lib/sequel/dataset/features.rb', line 139

def supports_window_functions?
  false
end

#to_csv(include_column_titles = true) ⇒ Object

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

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

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



549
550
551
552
553
554
555
556
 
# File 'lib/sequel/dataset/actions.rb', line 549

def to_csv(include_column_titles = true)
  n = naked
  cols = n.columns
  csv = ''
  csv << "#{cols.join(COMMA_SEPARATOR)}\r\n" if include_column_titles
  n.each{|r| csv << "#{cols.collect{|c| r[c]}.join(COMMA_SEPARATOR)}\r\n"}
  csv
end

#to_dot ⇒ Object

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



145
146
147
 
# File 'lib/sequel/extensions/to_dot.rb', line 145

def to_dot
  ToDot.output(self)
end

#to_hash(key_column, value_column = nil) ⇒ Object

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'}, ...}



577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
 
# File 'lib/sequel/dataset/actions.rb', line 577

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

#to_hash_groups(key_column, value_column = nil) ⇒ Object

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'}, ...], ...}



620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
 
# File 'lib/sequel/dataset/actions.rb', line 620

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

#truncate ⇒ Object

Truncates the dataset. Returns nil.

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



649
650
651
 
# File 'lib/sequel/dataset/actions.rb', line 649

def truncate
  execute_ddl(truncate_sql)
end

#truncate_sql ⇒ Object

Returns a TRUNCATE SQL query string. See truncate

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



151
152
153
154
155
156
157
158
159
 
# File 'lib/sequel/dataset/sql.rb', line 151

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]
    _truncate_sql(source_list(opts[:from]))
  end
end

#unbind ⇒ Object

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

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



827
828
829
830
831
 
# File 'lib/sequel/dataset/query.rb', line 827

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

#unfiltered ⇒ Object

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



837
838
839
 
# File 'lib/sequel/dataset/query.rb', line 837

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

#ungraphed ⇒ Object

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



239
240
241
 
# File 'lib/sequel/dataset/graph.rb', line 239

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

#ungrouped ⇒ Object

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



845
846
847
 
# File 'lib/sequel/dataset/query.rb', line 845

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

#union(dataset, opts = {}) ⇒ Object

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



865
866
867
868
 
# File 'lib/sequel/dataset/query.rb', line 865

def union(dataset, opts={})
  opts = {:all=>opts} unless opts.is_a?(Hash)
  compound_clone(:union, dataset, opts)
end

#unlimited ⇒ Object

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

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



873
874
875
 
# File 'lib/sequel/dataset/query.rb', line 873

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

#unordered ⇒ Object

Returns a copy of the dataset with no order.

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



880
881
882
 
# File 'lib/sequel/dataset/query.rb', line 880

def unordered
  order(nil)
end

#unused_table_alias(table_alias, used_aliases = []) ⇒ Object

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



190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
 
# File 'lib/sequel/dataset/misc.rb', line 190

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

#update(values = {}, &block) ⇒ Object

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



663
664
665
666
667
668
669
670
 
# File 'lib/sequel/dataset/actions.rb', line 663

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

#update_sql(values = {}) ⇒ Object

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.



168
169
170
171
172
 
# File 'lib/sequel/dataset/sql.rb', line 168

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

#where(*cond, &block) ⇒ Object

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

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

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



891
892
893
 
# File 'lib/sequel/dataset/query.rb', line 891

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

#window_function_sql_append(sql, function, window) ⇒ Object

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



695
696
697
698
699
 
# File 'lib/sequel/dataset/sql.rb', line 695

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

#window_sql_append(sql, opts) ⇒ Object

The SQL fragment for the given window’s options.

Raises:



654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
 
# File 'lib/sequel/dataset/sql.rb', line 654

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

#with(name, dataset, opts = {}) ⇒ Object

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

:args

Specify the arguments/columns for the CTE, should be an array of symbols.

:recursive

Specify that this is a recursive CTE

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

Raises:



903
904
905
906
907
908
909
910
911
 
# File 'lib/sequel/dataset/query.rb', line 903

def with(name, dataset, 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

#with_recursive(name, nonrecursive, recursive, opts = {}) ⇒ Object

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

:args

Specify the arguments/columns for the CTE, should be an array of symbols.

:union_all

Set to false to use UNION instead of UNION ALL combining the nonrecursive and recursive parts.

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

Raises:



930
931
932
933
934
935
936
937
938
939
940
941
 
# File 'lib/sequel/dataset/query.rb', line 930

def with_recursive(name, nonrecursive, recursive, 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

#with_sql(sql, *args) ⇒ Object

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)



955
956
957
958
959
960
961
962
 
# File 'lib/sequel/dataset/query.rb', line 955

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

#with_sql_delete(sql) ⇒ Object

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.



675
676
677
 
# File 'lib/sequel/dataset/actions.rb', line 675

def with_sql_delete(sql)
  execute_dui(sql)
end