Class Sequel::Dataset
In: lib/sequel/extensions/pagination.rb
lib/sequel/extensions/query.rb
lib/sequel/extensions/pretty_table.rb
lib/sequel/adapters/do.rb
lib/sequel/adapters/jdbc.rb
lib/sequel/adapters/utils/stored_procedures.rb
lib/sequel/adapters/utils/unsupported.rb
lib/sequel/dataset.rb
lib/sequel/dataset/convenience.rb
lib/sequel/dataset/prepared_statements.rb
lib/sequel/dataset/sql.rb
lib/sequel/dataset/graph.rb
lib/sequel/deprecated.rb
Parent: Object

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.

Methods added via metaprogramming

Some methods are added via metaprogramming:

  • ! methods - These methods are the same as their non-! counterparts, but they modify the receiver instead of returning a modified copy of the dataset.
  • inner_join, full_outer_join, right_outer_join, left_outer_join - This methods are shortcuts to join_table with the join type already specified.

Methods

<<   []   []=   add_graph_aliases   aliased_expression_sql   all   and   array_sql   as   avg   call   case_expression_sql   cast_sql   clone   column_all_sql   columns   columns!   complex_expression_sql   count   create_or_replace_view   create_view   dataset_classes   def_mutation_method   def_mutation_method   delete   delete_sql   distinct   each   each_page   each_page   empty?   except   exclude   exists   fetch_rows   fetch_rows   fetch_rows   filter   first   first_source   from   from_self   function_sql   get   graph   grep   group   group_and_count   group_by   having   import   inherited   insert   insert_multiple   insert_sql   inspect   intersect   interval   invert   irregular_function_sql   join_clause_sql   join_on_clause_sql   join_table   join_using_clause_sql   last   limit   literal   map   max   min   model_classes   multi_insert   multi_insert_sql   naked   new   options_overlap   or   order   order_by   order_more   ordered_expression_sql   paginate   paginate   placeholder_literal_string_sql   polymorphic_key   prepare   prepare   print   print   qualified_identifier_sql   query   query   quote_column_ref   quote_identifier   quote_identifiers?   quote_schema_table   quoted_identifier   range   reverse   reverse_order   schema_and_table   select   select_all   select_more   select_sql   server   set   set_defaults   set_graph_aliases   set_model   set_overrides   single_record   single_value   size   sql   subscript_sql   sum   symbol_to_column_ref   table_exists?   to_csv   to_hash   to_prepared_statement   to_table_reference   transform   transform_load   transform_save   unfiltered   union   uniq   unordered   upcase_identifiers=   upcase_identifiers?   update   update_sql   where   with_sql  

Included Modules

StoredProcedures Metaprogramming Enumerable

Classes and Modules

Module Sequel::Dataset::ArgumentMapper
Module Sequel::Dataset::Pagination
Module Sequel::Dataset::PreparedStatementMethods
Module Sequel::Dataset::QueryBlockCopy
Module Sequel::Dataset::SQLStandardDateFormat
Module Sequel::Dataset::StoredProcedureMethods
Module Sequel::Dataset::StoredProcedures
Module Sequel::Dataset::UnnumberedArgumentMapper
Module Sequel::Dataset::UnsupportedIntersectExcept
Module Sequel::Dataset::UnsupportedIntersectExceptAll
Module Sequel::Dataset::UnsupportedIsTrue

Constants

COLUMN_CHANGE_OPTS = [:select, :sql, :from, :join].freeze   The dataset options that require the removal of cached columns if changed.
MUTATION_METHODS = %w'add_graph_aliases and distinct exclude exists filter from from_self full_outer_join graph group group_and_count group_by having inner_join intersect invert join left_outer_join limit naked or order order_by order_more paginate query reject reverse reverse_order right_outer_join select select_all select_more set_defaults set_graph_aliases set_overrides sort sort_by unfiltered union unordered where with_sql'.collect{|x| x.to_sym}   All methods that should have a ! method added that modifies the receiver.
NOTIMPL_MSG = "This method must be overridden in Sequel adapters".freeze
COMMA_SEPARATOR = ', '.freeze
COUNT_OF_ALL_AS_COUNT = SQL::Function.new(:count, LiteralString.new('*'.freeze)).as(:count)
PREPARED_ARG_PLACEHOLDER = LiteralString.new('?').freeze
AND_SEPARATOR = " AND ".freeze
BOOL_FALSE = "'f'".freeze
BOOL_TRUE = "'t'".freeze
COLUMN_REF_RE1 = /\A([\w ]+)__([\w ]+)___([\w ]+)\z/.freeze
COLUMN_REF_RE2 = /\A([\w ]+)___([\w ]+)\z/.freeze
COLUMN_REF_RE3 = /\A([\w ]+)__([\w ]+)\z/.freeze
COUNT_FROM_SELF_OPTS = [:distinct, :group, :sql, :limit, :compounds]
IS_LITERALS = {nil=>'NULL'.freeze, true=>'TRUE'.freeze, false=>'FALSE'.freeze}.freeze
IS_OPERATORS = ::Sequel::SQL::ComplexExpression::IS_OPERATORS
N_ARITY_OPERATORS = ::Sequel::SQL::ComplexExpression::N_ARITY_OPERATORS
NULL = "NULL".freeze
QUESTION_MARK = '?'.freeze
STOCK_COUNT_OPTS = {:select => [LiteralString.new("COUNT(*)").freeze], :order => nil}.freeze
SELECT_CLAUSE_ORDER = %w'distinct columns from join where group having compounds order limit'.freeze
TWO_ARITY_OPERATORS = ::Sequel::SQL::ComplexExpression::TWO_ARITY_OPERATORS
WILDCARD = '*'.freeze
DATASET_CLASSES = []
STOCK_TRANSFORMS = { :marshal => [ # for backwards-compatibility we support also non-base64-encoded values. proc {|v| Marshal.load(v.unpack('m')[0]) rescue Marshal.load(v)}, proc {|v| [Marshal.dump(v)].pack('m')}

External Aliases

inner_join -> join

Attributes

db  [RW]  The database that corresponds to this dataset
identifier_input_method  [RW]  Set the method to call on identifiers going into the database for this dataset
identifier_output_method  [RW]  Set the method to call on identifiers coming the database for this dataset
opts  [RW]  The hash of options for this dataset, keys are symbols.
quote_identifiers  [W]  Whether to quote identifiers for this dataset
row_proc  [RW]  The row_proc for this database, should be a Proc that takes a single hash argument and returns the object you want each to return.

Public Class methods

[Source]

     # File lib/sequel/deprecated.rb, line 116
116:     def self.dataset_classes
117:       Deprecation.deprecate('Sequel::Dataset#dataset_classes', 'No replacement is planned')
118:       DATASET_CLASSES
119:     end

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

[Source]

     # File lib/sequel/dataset.rb, line 98
 98:     def self.def_mutation_method(*meths)
 99:       meths.each do |meth|
100:         class_eval("def #{meth}!(*args, &block); mutation_method(:#{meth}, *args, &block) end")
101:       end
102:     end

[Source]

     # File lib/sequel/deprecated.rb, line 121
121:     def self.inherited(c)
122:       DATASET_CLASSES << c
123:     end

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 adaptor should provide a subclass of Sequel::Dataset, and have the Database#dataset method return an instance of that class.

[Source]

    # File lib/sequel/dataset.rb, line 83
83:     def initialize(db, opts = nil)
84:       @db = db
85:       @quote_identifiers = db.quote_identifiers? if db.respond_to?(:quote_identifiers?)
86:       @identifier_input_method = db.identifier_input_method if db.respond_to?(:identifier_input_method)
87:       @identifier_output_method = db.identifier_output_method if db.respond_to?(:identifier_output_method)
88:       @opts = opts || {}
89:       @row_proc = nil
90:       @transform = nil
91:     end

Public Instance methods

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

[Source]

     # File lib/sequel/dataset.rb, line 108
108:     def <<(*args)
109:       insert(*args)
110:     end

Returns the first record matching the conditions. Examples:

  ds[:id=>1] => {:id=1}

[Source]

    # File lib/sequel/dataset/convenience.rb, line 9
 9:     def [](*conditions)
10:       Deprecation.deprecate('Using an Integer argument to Dataset#[] is deprecated and will raise an error in Sequel 3.0. Use Dataset#first.') if conditions.length == 1 and conditions.is_a?(Integer)
11:       Deprecation.deprecate('Using Dataset#[] without an argument is deprecated and will raise an error in Sequel 3.0. Use Dataset#first.') if conditions.length == 0
12:       first(*conditions)
13:     end

Update all records matching the conditions with the values specified. Examples:

  ds[:id=>1] = {:id=>2} # SQL: UPDATE ... SET id = 2 WHERE id = 1

[Source]

    # File lib/sequel/dataset/convenience.rb, line 19
19:     def []=(conditions, values)
20:       filter(conditions).update(values)
21:     end

Adds the give graph aliases to the list of graph aliases to use, unlike set_graph_aliases, which replaces the list. See set_graph_aliases.

[Source]

     # File lib/sequel/dataset/graph.rb, line 169
169:     def add_graph_aliases(graph_aliases)
170:       ds = select_more(*graph_alias_columns(graph_aliases))
171:       ds.opts[:graph_aliases] = (ds.opts[:graph_aliases] || {}).merge(graph_aliases)
172:       ds
173:     end

SQL fragment for the aliased expression

[Source]

    # File lib/sequel/dataset/sql.rb, line 31
31:     def aliased_expression_sql(ae)
32:       as_sql(literal(ae.expression), ae.aliaz)
33:     end

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.

[Source]

     # File lib/sequel/dataset.rb, line 121
121:     def all(opts = (defarg=true;nil), &block)
122:       Deprecation.deprecate("Calling Dataset#all with an argument is deprecated and will raise an error in Sequel 3.0.  Use dataset.clone(opts).all.") unless defarg
123:       a = []
124:       defarg ? each{|r| a << r} : each(opts){|r| a << r}
125:       post_load(a)
126:       a.each(&block) if block
127:       a
128:     end

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.

  ds.filter(:a).and(:b) # SQL: WHERE a AND b

[Source]

    # File lib/sequel/dataset/sql.rb, line 25
25:     def and(*cond, &block)
26:       raise(InvalidOperation, "No existing filter found.") unless @opts[:having] || @opts[:where]
27:       filter(*cond, &block)
28:     end

SQL fragment for the SQL array.

[Source]

    # File lib/sequel/dataset/sql.rb, line 36
36:     def array_sql(a)
37:       a.empty? ? '(NULL)' : "(#{expression_list(a)})"     
38:     end

Return the dataset as an aliased expression with the given alias. You can use this as a FROM or JOIN dataset, or as a column if this dataset returns a single row and column.

[Source]

     # File lib/sequel/dataset.rb, line 115
115:     def as(aliaz)
116:       ::Sequel::SQL::AliasedExpression.new(self, aliaz)
117:     end

Returns the average value for the given column.

[Source]

    # File lib/sequel/dataset/convenience.rb, line 24
24:     def avg(column)
25:       get{|o| o.avg(column)}
26:     end

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

[Source]

     # File lib/sequel/dataset/prepared_statements.rb, line 181
181:     def call(type, bind_variables={}, values=nil)
182:       prepare(type, nil, values).call(bind_variables)
183:     end

SQL fragment for specifying given CaseExpression.

[Source]

    # File lib/sequel/dataset/sql.rb, line 41
41:     def case_expression_sql(ce)
42:       sql = '(CASE '
43:       sql << "#{literal(ce.expression)} " if ce.expression
44:       ce.conditions.collect{ |c,r|
45:         sql << "WHEN #{literal(c)} THEN #{literal(r)} "
46:       }
47:       sql << "ELSE #{literal(ce.default)} END)"
48:     end

SQL fragment for the SQL CAST expression.

[Source]

    # File lib/sequel/dataset/sql.rb, line 51
51:     def cast_sql(expr, type)
52:       "CAST(#{literal(expr)} AS #{db.send(:type_literal_base, :type=>type)})"
53:     end

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.

[Source]

     # File lib/sequel/dataset.rb, line 133
133:     def clone(opts = {})
134:       c = super()
135:       c.opts = @opts.merge(opts)
136:       c.instance_variable_set(:@columns, nil) if opts.keys.any?{|o| COLUMN_CHANGE_OPTS.include?(o)}
137:       c
138:     end

SQL fragment for specifying all columns in a given table.

[Source]

    # File lib/sequel/dataset/sql.rb, line 56
56:     def column_all_sql(ca)
57:       "#{quote_schema_table(ca.table)}.*"
58:     end

Returns the columns in the result set in order. If the columns are currently cached, returns the cached value. Otherwise, a SELECT query is performed to get a single row. Adapters are expected to fill the columns cache with the column information when a query is performed. If the dataset does not have any rows, this may be an empty array depending on how the adapter is programmed.

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

[Source]

     # File lib/sequel/dataset.rb, line 149
149:     def columns
150:       return @columns if @columns
151:       ds = unfiltered.unordered.clone(:distinct => nil, :limit => 1)
152:       ds.each{break}
153:       @columns = ds.instance_variable_get(:@columns)
154:       @columns || []
155:     end

Remove the cached list of columns and do a SELECT query to find the columns.

[Source]

     # File lib/sequel/dataset.rb, line 159
159:     def columns!
160:       @columns = nil
161:       columns
162:     end

SQL fragment for complex expressions

[Source]

    # File lib/sequel/dataset/sql.rb, line 61
61:     def complex_expression_sql(op, args)
62:       case op
63:       when *IS_OPERATORS
64:         v = IS_LITERALS[args.at(1)] || raise(Error, 'Invalid argument used for IS operator')
65:         "(#{literal(args.at(0))} #{op} #{v})"
66:       when *TWO_ARITY_OPERATORS
67:         "(#{literal(args.at(0))} #{op} #{literal(args.at(1))})"
68:       when *N_ARITY_OPERATORS
69:         "(#{args.collect{|a| literal(a)}.join(" #{op} ")})"
70:       when :NOT
71:         "NOT #{literal(args.at(0))}"
72:       when :NOOP
73:         literal(args.at(0))
74:       when 'B~''B~'
75:         "~#{literal(args.at(0))}"
76:       else
77:         raise(Sequel::Error, "invalid operator #{op}")
78:       end
79:     end

Returns the number of records in the dataset.

[Source]

    # File lib/sequel/dataset/sql.rb, line 82
82:     def count
83:       options_overlap(COUNT_FROM_SELF_OPTS) ? from_self.count : clone(STOCK_COUNT_OPTS).single_value.to_i
84:     end

[Source]

     # File lib/sequel/deprecated.rb, line 192
192:     def create_or_replace_view(name)
193:       Sequel::Deprecation.deprecate('Sequel::Dataset#create_or_replace_view', 'Use Sequel::Database#create_or_replace_view')
194:       @db.create_or_replace_view(name, self)
195:     end

[Source]

     # File lib/sequel/deprecated.rb, line 187
187:     def create_view(name)
188:       Sequel::Deprecation.deprecate('Sequel::Dataset#create_view', 'Use Sequel::Database#create_view')
189:       @db.create_view(name, self)
190:     end

Add a mutation method to this dataset instance.

[Source]

     # File lib/sequel/dataset.rb, line 165
165:     def def_mutation_method(*meths)
166:       meths.each do |meth|
167:         instance_eval("def #{meth}!(*args, &block); mutation_method(:#{meth}, *args, &block) end")
168:       end
169:     end

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

[Source]

     # File lib/sequel/dataset.rb, line 173
173:     def delete(opts=(defarg=true;nil))
174:       Deprecation.deprecate("Calling Dataset#delete with an argument is deprecated and will raise an error in Sequel 3.0.  Use dataset.clone(opts).delete.") unless defarg
175:       execute_dui(defarg ? delete_sql : delete_sql(opts))
176:     end

Formats a DELETE statement using the given options and dataset options.

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

[Source]

     # File lib/sequel/dataset/sql.rb, line 90
 90:     def delete_sql(opts = (defarg=true;nil))
 91:       Deprecation.deprecate("Calling Dataset#delete_sql with an argument is deprecated and will raise an error in Sequel 3.0.  Use dataset.clone(opts).delete_sql.") unless defarg
 92:       opts = opts ? @opts.merge(opts) : @opts
 93: 
 94:       return static_sql(opts[:sql]) if opts[:sql]
 95: 
 96:       if opts[:group]
 97:         raise InvalidOperation, "Grouped datasets cannot be deleted from"
 98:       elsif opts[:from].is_a?(Array) && opts[:from].size > 1
 99:         raise InvalidOperation, "Joined datasets cannot be deleted from"
100:       end
101: 
102:       sql = "DELETE FROM #{source_list(opts[:from])}"
103: 
104:       if where = opts[:where]
105:         sql << " WHERE #{literal(where)}"
106:       end
107: 
108:       sql
109:     end

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.

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

[Source]

     # File lib/sequel/dataset/sql.rb, line 119
119:     def distinct(*args)
120:       clone(:distinct => args)
121:     end

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

[Source]

     # File lib/sequel/dataset.rb, line 180
180:     def each(opts = (defarg=true;nil), &block)
181:       Deprecation.deprecate("Calling Dataset#each with an argument is deprecated and will raise an error in Sequel 3.0.  Use dataset.clone(opts).each.") unless defarg
182:       if opts && opts.keys.any?{|o| COLUMN_CHANGE_OPTS.include?(o)}
183:         prev_columns = @columns
184:         begin
185:           defarg ? _each(&block) : _each(opts, &block)
186:         ensure
187:           @columns = prev_columns
188:         end
189:       else
190:         defarg ? _each(&block) : _each(opts, &block)
191:       end
192:       self
193:     end

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

[Source]

    # File lib/sequel/extensions/pagination.rb, line 16
16:     def each_page(page_size, &block)
17:       raise(Error, "You cannot paginate a dataset that already has a limit") if @opts[:limit]
18:       record_count = count
19:       total_pages = (record_count / page_size.to_f).ceil
20:       (1..total_pages).each{|page_no| yield paginate(page_no, page_size, record_count)}
21:       self
22:     end

[Source]

     # File lib/sequel/deprecated.rb, line 226
226:     def each_page(page_size, &block)
227:       Sequel::Deprecation.deprecate('Sequel::Dataset#each_page', 'require "sequel/extensions/pagination" first')
228:       raise(Error, "You cannot paginate a dataset that already has a limit") if @opts[:limit]
229:       record_count = count
230:       total_pages = (record_count / page_size.to_f).ceil
231:       (1..total_pages).each{|page_no| yield paginate(page_no, page_size, record_count)}
232:       self
233:     end

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

[Source]

    # File lib/sequel/dataset/convenience.rb, line 29
29:     def empty?
30:       get(1).nil?
31:     end

Adds an EXCEPT clause using a second dataset object. If all is true the clause used is EXCEPT ALL, which may return duplicate rows.

  DB[:items].except(DB[:other_items]).sql
  #=> "SELECT * FROM items EXCEPT SELECT * FROM other_items"

[Source]

     # File lib/sequel/dataset/sql.rb, line 128
128:     def except(dataset, all = false)
129:       compound_clone(:except, dataset, all)
130:     end

Performs the inverse of Dataset#filter.

  dataset.exclude(:category => 'software').sql #=>
    "SELECT * FROM items WHERE (category != 'software')"

[Source]

     # File lib/sequel/dataset/sql.rb, line 136
136:     def exclude(*cond, &block)
137:       clause = (@opts[:having] ? :having : :where)
138:       cond = cond.first if cond.size == 1
139:       cond = SQL::BooleanExpression.from_value_pairs(cond, :OR) if Sequel.condition_specifier?(cond)
140:       cond = filter_expr(cond, &block)
141:       cond = SQL::BooleanExpression.invert(cond)
142:       cond = SQL::BooleanExpression.new(:AND, @opts[clause], cond) if @opts[clause]
143:       clone(clause => cond)
144:     end

Returns an EXISTS clause for the dataset as a LiteralString.

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

[Source]

     # File lib/sequel/dataset/sql.rb, line 150
150:     def exists(opts = (defarg=true;nil))
151:       Deprecation.deprecate("Calling Dataset#exists with an argument is deprecated and will raise an error in Sequel 3.0.  Use dataset.clone(opts).exists.") unless defarg
152:       LiteralString.new("EXISTS (#{defarg ? select_sql : select_sql(opts)})")
153:     end

Executes a select query and fetches records, passing each record to the supplied block. The yielded records should be hashes with symbol keys.

[Source]

     # File lib/sequel/dataset.rb, line 197
197:     def fetch_rows(sql, &block)
198:       raise NotImplementedError, NOTIMPL_MSG
199:     end

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

[Source]

     # File lib/sequel/adapters/do.rb, line 184
184:       def fetch_rows(sql)
185:         execute(sql) do |reader|
186:           cols = @columns = reader.fields.map{|f| output_identifier(f)}
187:           while(reader.next!) do
188:             h = {}
189:             cols.zip(reader.values).each{|k, v| h[k] = v}
190:             yield h
191:           end
192:         end
193:         self
194:       end

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

[Source]

     # File lib/sequel/adapters/jdbc.rb, line 418
418:       def fetch_rows(sql, &block)
419:         execute(sql){|result| process_result_set(result, &block)}
420:         self
421:       end

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.
  • 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.

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

Examples:

  dataset.filter(:id => 3).sql #=>
    "SELECT * FROM items WHERE (id = 3)"
  dataset.filter('price < ?', 100).sql #=>
    "SELECT * FROM items WHERE price < 100"
  dataset.filter([[:id, (1,2,3)], [:id, 0..10]]).sql #=>
    "SELECT * FROM items WHERE ((id IN (1, 2, 3)) AND ((id >= 0) AND (id <= 10)))"
  dataset.filter('price < 100').sql #=>
    "SELECT * FROM items WHERE price < 100"
  dataset.filter(:active).sql #=>
    "SELECT * FROM items WHERE :active
  dataset.filter{|o| o.price < 100}.sql #=>
    "SELECT * FROM items WHERE (price < 100)"

Multiple filter calls can be chained for scoping:

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

See doc/dataset_filters.rdoc for more examples and details.

[Source]

     # File lib/sequel/dataset/sql.rb, line 202
202:     def filter(*cond, &block)
203:       _filter(@opts[:having] ? :having : :where, *cond, &block)
204:     end

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:

  ds.first => {:id=>7}
  ds.first(2) => [{:id=>6}, {:id=>4}]
  ds.order(:id).first(2) => [{:id=>1}, {:id=>2}]
  ds.first(:id=>2) => {:id=>2}
  ds.first("id = 3") => {:id=>3}
  ds.first("id = ?", 4) => {:id=>4}
  ds.first{|o| o.id > 2} => {:id=>5}
  ds.order(:id).first{|o| o.id > 2} => {:id=>3}
  ds.first{|o| o.id > 2} => {:id=>5}
  ds.first("id > ?", 4){|o| o.id < 6} => {:id=>5}
  ds.order(:id).first(2){|o| o.id < 2} => [{:id=>1}]

[Source]

    # File lib/sequel/dataset/convenience.rb, line 52
52:     def first(*args, &block)
53:       ds = block ? filter(&block) : self
54: 
55:       if args.empty?
56:         ds.single_record
57:       else
58:         args = (args.size == 1) ? args.first : args
59:         if Integer === args
60:           ds.limit(args).all
61:         else
62:           ds.filter(args).single_record
63:         end
64:       end
65:     end

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.

[Source]

     # File lib/sequel/dataset/sql.rb, line 208
208:     def first_source
209:       source = @opts[:from]
210:       if source.nil? || source.empty?
211:         raise Error, 'No source specified for query'
212:       end
213:       case s = source.first
214:       when Hash
215:         s.values.first
216:       when Symbol
217:         sch, table, aliaz = split_symbol(s)
218:         aliaz ? aliaz.to_sym : s
219:       else
220:         s
221:       end
222:     end

Returns a copy of the dataset with the source changed.

  dataset.from(:blah) # SQL: SELECT * FROM blah
  dataset.from(:blah, :foo) # SQL: SELECT * FROM blah, foo

[Source]

     # File lib/sequel/dataset/sql.rb, line 228
228:     def from(*source)
229:       clone(:from => source)
230:     end

Returns a dataset selecting from the current dataset.

  ds = DB[:items].order(:name)
  ds.sql #=> "SELECT * FROM items ORDER BY name"
  ds.from_self.sql #=> "SELECT * FROM (SELECT * FROM items ORDER BY name)"

[Source]

     # File lib/sequel/dataset/sql.rb, line 237
237:     def from_self
238:       fs = {}
239:       @opts.keys.each{|k| fs[k] = nil} 
240:       fs[:from] = [self]
241:       clone(fs)
242:     end

SQL fragment specifying an SQL function call

[Source]

     # File lib/sequel/dataset/sql.rb, line 245
245:     def function_sql(f)
246:       args = f.args
247:       "#{f.f}#{args.empty? ? '()' : literal(args)}"
248:     end

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

  ds.get(:id)
  ds.get{|o| o.sum(:id)}

[Source]

    # File lib/sequel/dataset/convenience.rb, line 72
72:     def get(column=nil, &block)
73:       raise(Error, 'must provide argument or block to Dataset#get, not both') if column && block
74:       (column ? select(column) : select(&block)).single_value
75:     end

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 or transform attributes 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 return a symbol or a dataset
  • join_conditions - Any condition(s) allowed by join_table.
  • options - A hash of graph options. The following options are currently used:
    • :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 join that makes it important to use graph instead of join.
    • :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.
  • block - A block that is passed to join_table.

[Source]

     # File lib/sequel/dataset/graph.rb, line 48
 48:     def graph(dataset, join_conditions = nil, options = {}, &block)
 49:       # Allow the use of a model, dataset, or symbol as the first argument
 50:       # Find the table name/dataset based on the argument
 51:       dataset = dataset.dataset if dataset.respond_to?(:dataset)
 52:       case dataset
 53:       when Symbol
 54:         table = dataset
 55:         dataset = @db[dataset]
 56:       when ::Sequel::Dataset
 57:         table = dataset.first_source
 58:       else
 59:         raise Error, "The dataset argument should be a symbol, dataset, or model"
 60:       end
 61: 
 62:       # Raise Sequel::Error with explanation that the table alias has been used
 63:       raise_alias_error = lambda do
 64:         raise(Error, "this #{options[:table_alias] ? 'alias' : 'table'} has already been been used, please specify " \
 65:           "#{options[:table_alias] ? 'a different alias' : 'an alias via the :table_alias option'}") 
 66:       end
 67: 
 68:       # Only allow table aliases that haven't been used
 69:       table_alias = options[:table_alias] || table
 70:       raise_alias_error.call if @opts[:graph] && @opts[:graph][:table_aliases] && @opts[:graph][:table_aliases].include?(table_alias)
 71: 
 72:       # Join the table early in order to avoid cloning the dataset twice
 73:       ds = join_table(options[:join_type] || :left_outer, table, join_conditions, :table_alias=>table_alias, :implicit_qualifier=>options[:implicit_qualifier], &block)
 74:       opts = ds.opts
 75: 
 76:       # Whether to include the table in the result set
 77:       add_table = options[:select] == false ? false : true
 78:       # Whether to add the columns to the list of column aliases
 79:       add_columns = !ds.opts.include?(:graph_aliases)
 80: 
 81:       # Setup the initial graph data structure if it doesn't exist
 82:       unless graph = opts[:graph]
 83:         master = ds.first_source
 84:         raise_alias_error.call if master == table_alias
 85:         # Master hash storing all .graph related information
 86:         graph = opts[:graph] = {}
 87:         # Associates column aliases back to tables and columns
 88:         column_aliases = graph[:column_aliases] = {}
 89:         # Associates table alias (the master is never aliased)
 90:         table_aliases = graph[:table_aliases] = {master=>self}
 91:         # Keep track of the alias numbers used
 92:         ca_num = graph[:column_alias_num] = Hash.new(0)
 93:         # All columns in the master table are never
 94:         # aliased, but are not included if set_graph_aliases
 95:         # has been used.
 96:         if add_columns
 97:           select = opts[:select] = []
 98:           columns.each do |column|
 99:             column_aliases[column] = [master, column]
100:             select.push(SQL::QualifiedIdentifier.new(master, column))
101:           end
102:         end
103:       end
104: 
105:       # Add the table alias to the list of aliases
106:       # Even if it isn't been used in the result set,
107:       # we add a key for it with a nil value so we can check if it
108:       # is used more than once
109:       table_aliases = graph[:table_aliases]
110:       table_aliases[table_alias] = add_table ? dataset : nil
111: 
112:       # Add the columns to the selection unless we are ignoring them
113:       if add_table && add_columns
114:         select = opts[:select]
115:         column_aliases = graph[:column_aliases]
116:         ca_num = graph[:column_alias_num]
117:         # Which columns to add to the result set
118:         cols = options[:select] || dataset.columns
119:         # If the column hasn't been used yet, don't alias it.
120:         # If it has been used, try table_column.
121:         # If that has been used, try table_column_N 
122:         # using the next value of N that we know hasn't been
123:         # used
124:         cols.each do |column|
125:           col_alias, identifier = if column_aliases[column]
126:             column_alias = "#{table_alias}_#{column}""#{table_alias}_#{column}"
127:             if column_aliases[column_alias]
128:               column_alias_num = ca_num[column_alias]
129:               column_alias = "#{column_alias}_#{column_alias_num}""#{column_alias}_#{column_alias_num}" 
130:               ca_num[column_alias] += 1
131:             end
132:             [column_alias, SQL::QualifiedIdentifier.new(table_alias, column).as(column_alias)]
133:           else
134:             [column, SQL::QualifiedIdentifier.new(table_alias, column)]
135:           end
136:           column_aliases[col_alias] = [table_alias, column]
137:           select.push(identifier)
138:         end
139:       end
140:       ds
141:     end

Pattern match any of the columns to any of the terms. The terms can be strings (which use LIKE) or regular expressions (which are only supported in some databases). See Sequel::SQL::StringExpression.like. Note that the total number of pattern matches will be cols.length * terms.length, which could cause performance issues.

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

[Source]

     # File lib/sequel/dataset/sql.rb, line 258
258:     def grep(cols, terms)
259:       filter(SQL::BooleanExpression.new(:OR, *Array(cols).collect{|c| SQL::StringExpression.like(c, *terms)}))
260:     end

Returns a copy of the dataset with the results grouped by the value of the given columns.

  dataset.group(:id) # SELECT * FROM items GROUP BY id
  dataset.group(:id, :name) # SELECT * FROM items GROUP BY id, name

[Source]

     # File lib/sequel/dataset/sql.rb, line 267
267:     def group(*columns)
268:       clone(:group => columns)
269:     end

Returns a dataset grouped by the given column with count by group, order by the count of records. Examples:

  ds.group_and_count(:name) => [{:name=>'a', :count=>1}, ...]
  ds.group_and_count(:first_name, :last_name) => [{:first_name=>'a', :last_name=>'b', :count=>1}, ...]

[Source]

    # File lib/sequel/dataset/convenience.rb, line 82
82:     def group_and_count(*columns)
83:       group(*columns).select(*(columns + [COUNT_OF_ALL_AS_COUNT])).order(:count)
84:     end
group_by(*columns)

Alias for group

Returns a copy of the dataset with the HAVING conditions changed. Raises an error if the dataset has not been grouped. See filter for argument types.

  dataset.group(:sum).having(:sum=>10) # SQL: SELECT * FROM items GROUP BY sum HAVING sum = 10

[Source]

     # File lib/sequel/dataset/sql.rb, line 276
276:     def having(*cond, &block)
277:       raise(InvalidOperation, "Can only specify a HAVING clause on a grouped dataset") unless @opts[:group]
278:       _filter(:having, *cond, &block)
279:     end

Inserts multiple records into the associated table. This method can be to efficiently insert a large amounts of records into a table. Inserts are automatically wrapped in a transaction.

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

  dataset.import([:x, :y], [[1, 2], [3, 4]])

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

  dataset.import([:x, :y], other_dataset.select(:a___x, :b___y))

The method also accepts a :slice or :commit_every option that specifies the number of records to insert per transaction. This is useful especially when inserting a large number of records, e.g.:

  # this will commit every 50 records
  dataset.import([:x, :y], [[1, 2], [3, 4], ...], :slice => 50)

[Source]

     # File lib/sequel/dataset/convenience.rb, line 104
104:     def import(*args)
105:       if args.empty?
106:         Sequel::Deprecation.deprecate('Calling Sequel::Dataset#import with no arguments', 'Use dataset.multi_insert([])')
107:         return
108:       elsif args[0].is_a?(Array) && args[1].is_a?(Array)
109:         columns, values, opts = *args
110:       elsif args[0].is_a?(Array) && args[1].is_a?(Dataset)
111:         table = @opts[:from].first
112:         columns, dataset = *args
113:         sql = "INSERT INTO #{quote_identifier(table)} (#{identifier_list(columns)}) VALUES #{literal(dataset)}"
114:         return @db.transaction{execute_dui(sql)}
115:       else
116:         Sequel::Deprecation.deprecate('Calling Sequel::Dataset#import with hashes', 'Use Sequel::Dataset#multi_insert')
117:         return multi_insert(*args)
118:       end
119:       # make sure there's work to do
120:       Sequel::Deprecation.deprecate('Calling Sequel::Dataset#import an empty column array is deprecated and will raise an error in Sequel 3.0.') if columns.empty?
121:       return if columns.empty? || values.empty?
122:       
123:       slice_size = opts && (opts[:commit_every] || opts[:slice])
124:       
125:       if slice_size
126:         values.each_slice(slice_size) do |slice|
127:           statements = multi_insert_sql(columns, slice)
128:           @db.transaction(opts){statements.each{|st| execute_dui(st)}}
129:         end
130:       else
131:         statements = multi_insert_sql(columns, values)
132:         @db.transaction{statements.each{|st| execute_dui(st)}}
133:       end
134:     end

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.

[Source]

     # File lib/sequel/dataset.rb, line 203
203:     def insert(*values)
204:       execute_insert(insert_sql(*values))
205:     end

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 possible faster version that inserts multiple records in one SQL statement.

[Source]

     # File lib/sequel/dataset/sql.rb, line 285
285:     def insert_multiple(array, &block)
286:       if block
287:         array.each {|i| insert(block[i])}
288:       else
289:         array.each {|i| insert(i)}
290:       end
291:     end

Formats an INSERT statement using the given values. If a hash is given, the resulting statement includes column names. If no values are given, the resulting statement includes a DEFAULT VALUES clause.

  dataset.insert_sql #=> 'INSERT INTO items DEFAULT VALUES'
  dataset.insert_sql(1,2,3) #=> 'INSERT INTO items VALUES (1, 2, 3)'
  dataset.insert_sql(:a => 1, :b => 2) #=>
    'INSERT INTO items (a, b) VALUES (1, 2)'

[Source]

     # File lib/sequel/dataset/sql.rb, line 301
301:     def insert_sql(*values)
302:       return static_sql(@opts[:sql]) if @opts[:sql]
303: 
304:       from = source_list(@opts[:from])
305:       case values.size
306:       when 0
307:         values = {}
308:       when 1
309:         vals = values.at(0)
310:         if [Hash, Dataset, Array].any?{|c| vals.is_a?(c)}
311:           values = vals
312:         elsif vals.respond_to?(:values)
313:           values = vals.values
314:         end
315:       end
316: 
317:       case values
318:       when Array
319:         if values.empty?
320:           insert_default_values_sql
321:         else
322:           "INSERT INTO #{from} VALUES #{literal(values)}"
323:         end
324:       when Hash
325:         values = @opts[:defaults].merge(values) if @opts[:defaults]
326:         values = values.merge(@opts[:overrides]) if @opts[:overrides]
327:         values = transform_save(values) if @transform
328:         if values.empty?
329:           insert_default_values_sql
330:         else
331:           fl, vl = [], []
332:           values.each do |k, v|
333:             fl << literal(String === k ? k.to_sym : k)
334:             vl << literal(v)
335:           end
336:           "INSERT INTO #{from} (#{fl.join(COMMA_SEPARATOR)}) VALUES (#{vl.join(COMMA_SEPARATOR)})"
337:         end
338:       when Dataset
339:         "INSERT INTO #{from} #{literal(values)}"
340:       end
341:     end

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

[Source]

     # File lib/sequel/dataset.rb, line 209
209:     def inspect
210:       "#<#{self.class}: #{sql.inspect}>"
211:     end

Adds an INTERSECT clause using a second dataset object. If all is true the clause used is INTERSECT ALL, which may return duplicate rows.

  DB[:items].intersect(DB[:other_items]).sql
  #=> "SELECT * FROM items INTERSECT SELECT * FROM other_items"

[Source]

     # File lib/sequel/dataset/sql.rb, line 348
348:     def intersect(dataset, all = false)
349:       compound_clone(:intersect, dataset, all)
350:     end

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

[Source]

     # File lib/sequel/dataset/convenience.rb, line 138
138:     def interval(column)
139:       get{|o| o.max(column) - o.min(column)}
140:     end

Inverts the current filter

  dataset.filter(:category => 'software').invert.sql #=>
    "SELECT * FROM items WHERE (category != 'software')"

[Source]

     # File lib/sequel/dataset/sql.rb, line 356
356:     def invert
357:       having, where = @opts[:having], @opts[:where]
358:       raise(Error, "No current filter") unless having || where
359:       o = {}
360:       o[:having] = SQL::BooleanExpression.invert(having) if having
361:       o[:where] = SQL::BooleanExpression.invert(where) if where
362:       clone(o)
363:     end

SQL fragment specifying an Irregular (cast/extract) SQL function call

[Source]

     # File lib/sequel/dataset/sql.rb, line 366
366:     def irregular_function_sql(f)
367:       "#{f.f}(#{literal(f.arg1)} #{f.joiner} #{literal(f.arg2)})"
368:     end

SQL fragment specifying a JOIN clause without ON or USING.

[Source]

     # File lib/sequel/dataset/sql.rb, line 371
371:     def join_clause_sql(jc)
372:       table = jc.table
373:       table_alias = jc.table_alias
374:       table_alias = nil if table == table_alias
375:       tref = table_ref(table)
376:       " #{join_type_sql(jc.join_type)} #{table_alias ? as_sql(tref, table_alias) : tref}"
377:     end

SQL fragment specifying a JOIN clause with ON.

[Source]

     # File lib/sequel/dataset/sql.rb, line 380
380:     def join_on_clause_sql(jc)
381:       "#{join_clause_sql(jc)} ON #{literal(filter_expr(jc.on))}"
382:     end

Returns a joined dataset. Uses 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 with all two pairs - 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 a 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 blockless filter 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_qualifer - 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.

[Source]

     # File lib/sequel/dataset/sql.rb, line 419
419:     def join_table(type, table, expr=nil, options={}, &block)
420:       if [Symbol, String].any?{|c| options.is_a?(c)}
421:         table_alias = options
422:         last_alias = nil 
423:       else
424:         table_alias = options[:table_alias]
425:         last_alias = options[:implicit_qualifier]
426:       end
427:       if Dataset === table
428:         if table_alias.nil?
429:           table_alias_num = (@opts[:num_dataset_sources] || 0) + 1
430:           table_alias = "t#{table_alias_num}"
431:         end
432:         table_name = table_alias
433:       else
434:         table = table.table_name if table.respond_to?(:table_name)
435:         table_name = table_alias || table
436:       end
437: 
438:       join = if expr.nil? and !block_given?
439:         SQL::JoinClause.new(type, table, table_alias)
440:       elsif Array === expr and !expr.empty? and expr.all?{|x| Symbol === x}
441:         raise(Sequel::Error, "can't use a block if providing an array of symbols as expr") if block_given?
442:         SQL::JoinUsingClause.new(expr, type, table, table_alias)
443:       else
444:         last_alias ||= @opts[:last_joined_table] || (first_source.is_a?(Dataset) ? 't1' : first_source)
445:         if Sequel.condition_specifier?(expr)
446:           expr = expr.collect do |k, v|
447:             k = qualified_column_name(k, table_name) if k.is_a?(Symbol)
448:             v = qualified_column_name(v, last_alias) if v.is_a?(Symbol)
449:             [k,v]
450:           end
451:         end
452:         if block_given?
453:           expr2 = yield(table_name, last_alias, @opts[:join] || [])
454:           expr = expr ? SQL::BooleanExpression.new(:AND, expr, expr2) : expr2
455:         end
456:         SQL::JoinOnClause.new(expr, type, table, table_alias)
457:       end
458: 
459:       opts = {:join => (@opts[:join] || []) + [join], :last_joined_table => table_name}
460:       opts[:num_dataset_sources] = table_alias_num if table_alias_num
461:       clone(opts)
462:     end

SQL fragment specifying a JOIN clause with USING.

[Source]

     # File lib/sequel/dataset/sql.rb, line 385
385:     def join_using_clause_sql(jc)
386:       "#{join_clause_sql(jc)} USING (#{column_list(jc.using)})"
387:     end

Reverses the order and then runs first. 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.

[Source]

     # File lib/sequel/dataset/convenience.rb, line 146
146:     def last(*args, &block)
147:       raise(Error, 'No order specified') unless @opts[:order]
148:       reverse.first(*args, &block)
149:     end

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.

  dataset.limit(10) # SQL: SELECT * FROM items LIMIT 10
  dataset.limit(10, 20) # SQL: SELECT * FROM items LIMIT 10 OFFSET 20

[Source]

     # File lib/sequel/dataset/sql.rb, line 470
470:     def limit(l, o = nil)
471:       return from_self.limit(l, o) if @opts[:sql]
472: 
473:       if Range === l
474:         o = l.first
475:         l = l.last - l.first + (l.exclude_end? ? 0 : 1)
476:       end
477:       l = l.to_i
478:       raise(Error, 'Limits must be greater than or equal to 1') unless l >= 1
479:       opts = {:limit => l}
480:       if o
481:         o = o.to_i
482:         raise(Error, 'Offsets must be greater than or equal to 0') unless o >= 0
483:         opts[:offset] = o
484:       end
485:       clone(opts)
486:     end

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

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

If an unsupported object is given, an exception is raised.

[Source]

     # File lib/sequel/dataset/sql.rb, line 498
498:     def literal(v)
499:       case v
500:       when String
501:         return v if v.is_a?(LiteralString)
502:         v.is_a?(SQL::Blob) ? literal_blob(v) : literal_string(v)
503:       when Symbol
504:         literal_symbol(v)
505:       when Integer
506:         literal_integer(v)
507:       when Hash
508:         literal_hash(v)
509:       when SQL::Expression
510:         literal_expression(v)
511:       when Float
512:         literal_float(v)
513:       when BigDecimal
514:         literal_big_decimal(v)
515:       when NilClass
516:         NULL
517:       when TrueClass
518:         literal_true
519:       when FalseClass
520:         literal_false
521:       when Array
522:         literal_array(v)
523:       when Time
524:         literal_time(v)
525:       when DateTime
526:         literal_datetime(v)
527:       when Date
528:         literal_date(v)
529:       when Dataset
530:         literal_dataset(v)
531:       else
532:         literal_other(v)
533:       end
534:     end

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

  ds.map(:id) => [1, 2, 3, ...]
  ds.map{|r| r[:id] * 2} => [2, 4, 6, ...]

[Source]

     # File lib/sequel/dataset/convenience.rb, line 157
157:     def map(column=nil, &block)
158:       Deprecation.deprecate('Using Dataset#map with an argument and a block is deprecated and will raise an error in Sequel 3.0. Use an argument or a block, not both.') if column && block
159:       if column
160:         super(){|r| r[column]}
161:       else
162:         super(&block)
163:       end
164:     end

Returns the maximum value for the given column.

[Source]

     # File lib/sequel/dataset/convenience.rb, line 167
167:     def max(column)
168:       get{|o| o.max(column)}
169:     end

Returns the minimum value for the given column.

[Source]

     # File lib/sequel/dataset/convenience.rb, line 172
172:     def min(column)
173:       get{|o| o.min(column)}
174:     end

[Source]

     # File lib/sequel/deprecated.rb, line 135
135:     def model_classes
136:       Deprecation.deprecate('Sequel::Dataset#model_classes', 'Sequel::Model datasets no longer set this information')
137:       @opts[:models]
138:     end

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

  dataset.multi_insert([{:x => 1}, {:x => 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.

You can also use the :slice or :commit_every option that import accepts.

[Source]

     # File lib/sequel/dataset/convenience.rb, line 186
186:     def multi_insert(*args)
187:       if args.empty?
188:         Sequel::Deprecation.deprecate('Calling Sequel::Dataset#multi_insert with no arguments', 'Use dataset.multi_insert([])')
189:         return
190:       elsif args[0].is_a?(Array) && (args[1].is_a?(Array) || args[1].is_a?(Dataset))
191:         Sequel::Deprecation.deprecate('Calling Sequel::Dataset#multi_insert with an array of columns and an array of arrays of values', 'Use Sequel::Dataset#import')
192:        return import(*args)
193:       else
194:         # we assume that an array of hashes is given
195:         hashes, opts = *args
196:         return if hashes.empty?
197:         columns = hashes.first.keys
198:         # convert the hashes into arrays
199:         values = hashes.map {|h| columns.map {|c| h[c]}}
200:       end
201:       import(columns, values, opts)
202:     end

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

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

[Source]

     # File lib/sequel/dataset/sql.rb, line 542
542:     def multi_insert_sql(columns, values)
543:       s = "INSERT INTO #{source_list(@opts[:from])} (#{identifier_list(columns)}) VALUES "
544:       values.map{|r| s + literal(r)}
545:     end

Returns a naked dataset clone - i.e. a dataset that returns records as hashes instead of calling the row proc.

[Source]

     # File lib/sequel/dataset.rb, line 215
215:     def naked
216:       ds = clone
217:       ds.row_proc = nil
218:       ds
219:     end

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

  dataset.filter(:a).or(:b) # SQL: SELECT * FROM items WHERE a OR b

[Source]

     # File lib/sequel/dataset/sql.rb, line 551
551:     def or(*cond, &block)
552:       clause = (@opts[:having] ? :having : :where)
553:       raise(InvalidOperation, "No existing filter found.") unless @opts[clause]
554:       cond = cond.first if cond.size == 1
555:       clone(clause => SQL::BooleanExpression.new(:OR, @opts[clause], filter_expr(cond, &block)))
556:     end

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

  ds.order(:name).sql #=> 'SELECT * FROM items ORDER BY name'
  ds.order(:a, :b).sql #=> 'SELECT * FROM items ORDER BY a, b'
  ds.order('a + b'.lit).sql #=> 'SELECT * FROM items ORDER BY a + b'
  ds.order(:a + :b).sql #=> 'SELECT * FROM items ORDER BY (a + b)'
  ds.order(:name.desc).sql #=> 'SELECT * FROM items ORDER BY name DESC'
  ds.order(:name.asc).sql #=> 'SELECT * FROM items ORDER BY name ASC'
  ds.order{|o| o.sum(:name)}.sql #=> 'SELECT * FROM items ORDER BY sum(name)'
  ds.order(nil).sql #=> 'SELECT * FROM items'

[Source]

     # File lib/sequel/dataset/sql.rb, line 571
571:     def order(*columns, &block)
572:       columns += Array(virtual_row_block_call(block)) if block
573:       clone(:order => (columns.compact.empty?) ? nil : columns)
574:     end
order_by(*columns, &block)

Alias for order

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

  ds.order(:a).order(:b).sql #=> 'SELECT * FROM items ORDER BY b'
  ds.order(:a).order_more(:b).sql #=> 'SELECT * FROM items ORDER BY a, b'

[Source]

     # File lib/sequel/dataset/sql.rb, line 582
582:     def order_more(*columns, &block)
583:       order(*Array(@opts[:order]).concat(columns), &block)
584:     end

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

[Source]

     # File lib/sequel/dataset/sql.rb, line 588
588:     def ordered_expression_sql(oe)
589:       "#{literal(oe.expression)} #{oe.descending ? 'DESC' : 'ASC'}"
590:     end

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

[Source]

    # File lib/sequel/extensions/pagination.rb, line 7
 7:     def paginate(page_no, page_size, record_count=nil)
 8:       raise(Error, "You cannot paginate a dataset that already has a limit") if @opts[:limit]
 9:       paginated = limit(page_size, (page_no - 1) * page_size)
10:       paginated.extend(Pagination)
11:       paginated.set_pagination_info(page_no, page_size, record_count || count)
12:     end

[Source]

     # File lib/sequel/deprecated.rb, line 217
217:     def paginate(page_no, page_size, record_count=nil)
218:       Sequel::Deprecation.deprecate('Sequel::Dataset#paginate', 'require "sequel/extensions/pagination" first')
219:       require "sequel/extensions/pagination"
220:       raise(Error, "You cannot paginate a dataset that already has a limit") if @opts[:limit]
221:       paginated = limit(page_size, (page_no - 1) * page_size)
222:       paginated.extend(Pagination)
223:       paginated.set_pagination_info(page_no, page_size, record_count || count)
224:     end

SQL fragment for a literal string with placeholders

[Source]

     # File lib/sequel/dataset/sql.rb, line 593
593:     def placeholder_literal_string_sql(pls)
594:       args = pls.args.dup
595:       s = pls.str.gsub(QUESTION_MARK){literal(args.shift)}
596:       s = "(#{s})" if pls.parens
597:       s
598:     end

[Source]

     # File lib/sequel/deprecated.rb, line 140
140:     def polymorphic_key
141:       Deprecation.deprecate('Sequel::Dataset#polymorphic_key', 'Sequel::Model datasets no longer set this information')
142:       @opts[:polymorphic_key]
143:     end

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

[Source]

     # File lib/sequel/adapters/jdbc.rb, line 425
425:       def prepare(type, name=nil, values=nil)
426:         ps = to_prepared_statement(type, values)
427:         ps.extend(PreparedStatementMethods)
428:         if name
429:           ps.prepared_statement_name = name
430:           db.prepared_statements[name] = ps
431:         end
432:         ps
433:       end

Prepare an SQL statement for later execution. This returns a clone of the dataset extended with PreparedStatementMethods, on which you can call call with the hash of bind variables to do substitution. The prepared statement is also stored in the associated database. The following usage is identical:

  ps = prepare(:select, :select_by_name)
  ps.call(:name=>'Blah')
  db.call(:select_by_name, :name=>'Blah')

[Source]

     # File lib/sequel/dataset/prepared_statements.rb, line 194
194:     def prepare(type, name=nil, values=nil)
195:       ps = to_prepared_statement(type, values)
196:       db.prepared_statements[name] = ps if name
197:       ps
198:     end

[Source]

     # File lib/sequel/deprecated.rb, line 244
244:     def print(*cols)
245:       Sequel::Deprecation.deprecate('Sequel::Dataset#print', 'require "sequel/extensions/pretty_table" first')
246:       Sequel::PrettyTable.print(naked.all, cols.empty? ? columns : cols)
247:     end

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

[Source]

   # File lib/sequel/extensions/pretty_table.rb, line 4
4:     def print(*cols)
5:       Sequel::PrettyTable.print(naked.all, cols.empty? ? columns : cols)
6:     end

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

[Source]

     # File lib/sequel/dataset/sql.rb, line 602
602:     def qualified_identifier_sql(qcr)
603:       [qcr.table, qcr.column].map{|x| [SQL::QualifiedIdentifier, SQL::Identifier, Symbol].any?{|c| x.is_a?(c)} ? literal(x) : quote_identifier(x)}.join('.')
604:     end

[Source]

     # File lib/sequel/deprecated.rb, line 235
235:     def query(&block)
236:       Sequel::Deprecation.deprecate('Sequel::Dataset#each_page', 'require "sequel/extensions/query" first')
237:       require "sequel/extensions/query"
238:       copy = clone({})
239:       copy.extend(QueryBlockCopy)
240:       copy.instance_eval(&block)
241:       clone(copy.opts)
242:     end

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

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

Which is the same as:

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

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

[Source]

    # File lib/sequel/extensions/query.rb, line 26
26:     def query(&block)
27:       copy = clone({})
28:       copy.extend(QueryBlockCopy)
29:       copy.instance_eval(&block)
30:       clone(copy.opts)
31:     end

[Source]

     # File lib/sequel/deprecated.rb, line 207
207:     def quote_column_ref(name)
208:       Sequel::Deprecation.deprecate('Sequel::Dataset#quote_column_ref', 'Use Sequel::Dataset#quote_identifier')
209:       quote_identifier(name)
210:     end

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

[Source]

     # File lib/sequel/dataset/sql.rb, line 609
609:     def quote_identifier(name)
610:       return name if name.is_a?(LiteralString)
611:       name = input_identifier(name)
612:       name = quoted_identifier(name) if quote_identifiers?
613:       name
614:     end

Whether this dataset quotes identifiers.

[Source]

     # File lib/sequel/dataset.rb, line 222
222:     def quote_identifiers?
223:       @quote_identifiers
224:     end

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

[Source]

     # File lib/sequel/dataset/sql.rb, line 618
618:     def quote_schema_table(table)
619:       schema, table = schema_and_table(table)
620:       "#{"#{quote_identifier(schema)}." if schema}#{quote_identifier(table)}"
621:     end

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

[Source]

     # File lib/sequel/dataset/sql.rb, line 626
626:     def quoted_identifier(name)
627:       "\"#{name.to_s.gsub('"', '""')}\""
628:     end

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

[Source]

     # File lib/sequel/dataset/convenience.rb, line 206
206:     def range(column)
207:       if r = select{|o| [o.min(column).as(:v1), o.max(column).as(:v2)]}.first
208:         (r[:v1]..r[:v2])
209:       end
210:     end
reverse(*order)

Alias for reverse_order

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

[Source]

     # File lib/sequel/dataset/sql.rb, line 632
632:     def reverse_order(*order)
633:       order(*invert_order(order.empty? ? @opts[:order] : order))
634:     end

Split the schema information from the table

[Source]

     # File lib/sequel/dataset/sql.rb, line 638
638:     def schema_and_table(table_name)
639:       sch = db.default_schema if db
640:       case table_name
641:       when Symbol
642:         s, t, a = split_symbol(table_name)
643:         [s||sch, t]
644:       when SQL::QualifiedIdentifier
645:         [table_name.table, table_name.column]
646:       when SQL::Identifier
647:         [sch, table_name.value]
648:       when String
649:         [sch, table_name]
650:       else
651:         raise Error, 'table_name should be a Symbol, SQL::QualifiedIdentifier, SQL::Identifier, or String'
652:       end
653:     end

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.

  dataset.select(:a) # SELECT a FROM items
  dataset.select(:a, :b) # SELECT a, b FROM items
  dataset.select{|o| o.a, o.sum(:b)} # SELECT a, sum(b) FROM items

[Source]

     # File lib/sequel/dataset/sql.rb, line 662
662:     def select(*columns, &block)
663:       columns += Array(virtual_row_block_call(block)) if block
664:       clone(:select => columns)
665:     end

Returns a copy of the dataset selecting the wildcard.

  dataset.select(:a).select_all # SELECT * FROM items

[Source]

     # File lib/sequel/dataset/sql.rb, line 670
670:     def select_all
671:       clone(:select => nil)
672:     end

Returns a copy of the dataset with the given columns added to the existing selected columns.

  dataset.select(:a).select(:b) # SELECT b FROM items
  dataset.select(:a).select_more(:b) # SELECT a, b FROM items

[Source]

     # File lib/sequel/dataset/sql.rb, line 679
679:     def select_more(*columns, &block)
680:       select(*Array(@opts[:select]).concat(columns), &block)
681:     end

Formats a SELECT statement

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

[Source]

     # File lib/sequel/dataset/sql.rb, line 686
686:     def select_sql(opts = (defarg=true;nil))
687:       Deprecation.deprecate("Calling Dataset#select_sql with an argument is deprecated and will raise an error in Sequel 3.0.  Use dataset.clone(opts).select_sql.") unless defarg
688:       opts = opts ? @opts.merge(opts) : @opts
689:       return static_sql(opts[:sql]) if opts[:sql]
690:       sql = 'SELECT'
691:       select_clause_order.each{|x| send("select_#{x}_sql", sql, opts)}
692:       sql
693:     end

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 (which is SELECT uses :read_only database and all other queries use the :default database).

[Source]

     # File lib/sequel/dataset.rb, line 229
229:     def server(servr)
230:       clone(:server=>servr)
231:     end

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

[Source]

     # File lib/sequel/dataset.rb, line 235
235:     def set(*args)
236:       update(*args)
237:     end

Set the default values for insert and update statements. The values passed to insert or update are merged into this hash.

[Source]

     # File lib/sequel/dataset.rb, line 241
241:     def set_defaults(hash)
242:       clone(:defaults=>(@opts[:defaults]||{}).merge(hash))
243:     end

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. Example:

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

Arguments:

  • graph_aliases - Should be a hash with keys being symbols of column aliases, and values being arrays with two or three elements. The first element of the array should be the table alias symbol, and the second should be the actual column name symbol. If the array has a third element, it is used as the value returned, instead of table_alias.column_name.

[Source]

     # File lib/sequel/dataset/graph.rb, line 160
160:     def set_graph_aliases(graph_aliases)
161:       ds = select(*graph_alias_columns(graph_aliases))
162:       ds.opts[:graph_aliases] = graph_aliases
163:       ds
164:     end

[Source]

     # File lib/sequel/deprecated.rb, line 145
145:     def set_model(key, *args)
146:       Deprecation.deprecate('Sequel::Dataset#set_model', 'Use Sequel::Dataset#set_row_proc with an appropriate row proc')
147:       # This code is more verbose then necessary for performance reasons
148:       case key
149:       when nil # set_model(nil) => no argument provided, so the dataset is denuded
150:         @opts.merge!(:naked => true, :models => nil, :polymorphic_key => nil)
151:         self.row_proc = nil
152:       when Class
153:         # isomorphic model
154:         @opts.merge!(:naked => nil, :models => {nil => key}, :polymorphic_key => nil)
155:         if key.respond_to?(:load)
156:           # the class has a values setter method, so we use it
157:           self.row_proc = proc{|h| key.load(h, *args)}
158:         else
159:           # otherwise we just pass the hash to the constructor
160:           self.row_proc = proc{|h| key.new(h, *args)}
161:         end
162:       when Symbol
163:         # polymorphic model
164:         hash = args.shift || raise(ArgumentError, "No class hash supplied for polymorphic model")
165:         @opts.merge!(:naked => true, :models => hash, :polymorphic_key => key)
166:         if (hash.empty? ? (hash[nil] rescue nil) : hash.values.first).respond_to?(:load)
167:           # the class has a values setter method, so we use it
168:           self.row_proc = proc do |h|
169:             c = hash[h[key]] || hash[nil] || \
170:               raise(Error, "No matching model class for record (#{polymorphic_key} => #{h[polymorphic_key].inspect})")
171:             c.load(h, *args)
172:           end
173:         else
174:           # otherwise we just pass the hash to the constructor
175:           self.row_proc = proc do |h|
176:             c = hash[h[key]] || hash[nil] || \
177:               raise(Error, "No matching model class for record (#{polymorphic_key} => #{h[polymorphic_key].inspect})")
178:             c.new(h, *args)
179:           end
180:         end
181:       else
182:         raise ArgumentError, "Invalid model specified"
183:       end
184:       self
185:     end

Set values that override hash arguments given to insert and update statements. This hash is merged into the hash provided to insert or update.

[Source]

     # File lib/sequel/dataset.rb, line 247
247:     def set_overrides(hash)
248:       clone(:overrides=>hash.merge(@opts[:overrides]||{}))
249:     end

Returns the first record in the dataset.

[Source]

     # File lib/sequel/dataset/convenience.rb, line 213
213:     def single_record(opts = (defarg=true;nil))
214:       Deprecation.deprecate("Calling Dataset#single_record with an argument is deprecated and will raise an error in Sequel 3.0.  Use dataset.clone(opts).single_record.") unless defarg
215:       ds = clone(:limit=>1)
216:       opts = opts.merge(:limit=>1) if opts and opts[:limit]
217:       defarg ? ds.each{|r| return r} : ds.each(opts){|r| return r}
218:       nil
219:     end

Returns the first value of the first record in the dataset. Returns nil if dataset is empty.

[Source]

     # File lib/sequel/dataset/convenience.rb, line 223
223:     def single_value(opts = (defarg=true;nil))
224:       Deprecation.deprecate("Calling Dataset#single_value with an argument is deprecated and will raise an error in Sequel 3.0.  Use dataset.clone(opts).single_value.") unless defarg
225:       ds = naked.clone(:graph=>false)
226:       if r = (defarg ? ds.single_record : ds.single_record(opts))
227:         r.values.first
228:       end
229:     end

[Source]

     # File lib/sequel/deprecated.rb, line 197
197:     def size
198:       Sequel::Deprecation.deprecate('Sequel::Dataset#size', 'Use Sequel::Dataset#count')
199:       count
200:     end

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

[Source]

     # File lib/sequel/dataset/sql.rb, line 696
696:     def sql(opts = (defarg=true;nil))
697:       Deprecation.deprecate("Calling Dataset#select_sql with an argument is deprecated and will raise an error in Sequel 3.0.  Use dataset.clone(opts).select_sql.") unless defarg
698:       defarg ? select_sql : select_sql(opts)
699:     end

SQL fragment for specifying subscripts (SQL arrays)

[Source]

     # File lib/sequel/dataset/sql.rb, line 702
702:     def subscript_sql(s)
703:       "#{s.f}[#{s.sub.join(COMMA_SEPARATOR)}]"
704:     end

Returns the sum for the given column.

[Source]

     # File lib/sequel/dataset/convenience.rb, line 232
232:     def sum(column)
233:       get{|o| o.sum(column)}
234:     end

[Source]

     # File lib/sequel/deprecated.rb, line 212
212:     def symbol_to_column_ref(sym)
213:       Sequel::Deprecation.deprecate('Sequel::Dataset#symbol_to_column_ref', 'Use Sequel::Dataset#literal')
214:       literal_symbol(sym)
215:     end

Returns true if the table exists. Will raise an error if the dataset has fixed SQL or selects from another dataset or more than one table.

[Source]

     # File lib/sequel/dataset/convenience.rb, line 239
239:     def table_exists?
240:       raise(Sequel::Error, "this dataset has fixed SQL") if @opts[:sql]
241:       raise(Sequel::Error, "this dataset selects from multiple sources") if @opts[:from].size != 1
242:       t = @opts[:from].first
243:       raise(Sequel::Error, "this dataset selects from a sub query") if t.is_a?(Dataset)
244:       @db.table_exists?(t)
245:     end

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.

[Source]

     # File lib/sequel/dataset/convenience.rb, line 255
255:     def to_csv(include_column_titles = true)
256:       n = naked
257:       cols = n.columns
258:       csv = ''
259:       csv << "#{cols.join(COMMA_SEPARATOR)}\r\n" if include_column_titles
260:       n.each{|r| csv << "#{cols.collect{|c| r[c]}.join(COMMA_SEPARATOR)}\r\n"}
261:       csv
262:     end

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.

[Source]

     # File lib/sequel/dataset/convenience.rb, line 268
268:     def to_hash(key_column, value_column = nil)
269:       inject({}) do |m, r|
270:         m[r[key_column]] = value_column ? r[value_column] : r
271:         m
272:       end
273:     end

[Source]

     # File lib/sequel/deprecated.rb, line 249
249:     def transform(t)
250:       Sequel::Deprecation.deprecate('Sequel::Dataset#transform', 'There is no replacement.')
251:       @transform = t
252:       t.each do |k, v|
253:         case v
254:         when Array
255:           if (v.size != 2) || !v.first.is_a?(Proc) && !v.last.is_a?(Proc)
256:             raise Error::InvalidTransform, "Invalid transform specified"
257:           end
258:         else
259:           unless v = STOCK_TRANSFORMS[v]
260:             raise Error::InvalidTransform, "Invalid transform specified"
261:           else
262:             t[k] = v
263:           end
264:         end
265:       end
266:       self
267:     end

[Source]

     # File lib/sequel/deprecated.rb, line 269
269:     def transform_load(r)
270:       r.inject({}) do |m, kv|
271:         k, v = *kv
272:         m[k] = (tt = @transform[k]) ? tt[0][v] : v
273:         m
274:       end
275:     end

[Source]

     # File lib/sequel/deprecated.rb, line 277
277:     def transform_save(r)
278:       r.inject({}) do |m, kv|
279:         k, v = *kv
280:         m[k] = (tt = @transform[k]) ? tt[1][v] : v
281:         m
282:       end
283:     end

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

  dataset.group(:a).having(:a=>1).where(:b).unfiltered # SELECT * FROM items

[Source]

     # File lib/sequel/dataset/sql.rb, line 709
709:     def unfiltered
710:       clone(:where => nil, :having => nil)
711:     end

Adds a UNION clause using a second dataset object. If all is true the clause used is UNION ALL, which may return duplicate rows.

  DB[:items].union(DB[:other_items]).sql
  #=> "SELECT * FROM items UNION SELECT * FROM other_items"

[Source]

     # File lib/sequel/dataset/sql.rb, line 718
718:     def union(dataset, all = false)
719:       compound_clone(:union, dataset, all)
720:     end

[Source]

     # File lib/sequel/deprecated.rb, line 202
202:     def uniq(*args)
203:       Sequel::Deprecation.deprecate('Sequel::Dataset#uniq', 'Use Sequel::Dataset#distinct')
204:       distinct(*args)
205:     end

Returns a copy of the dataset with no order.

  dataset.order(:a).unordered # SELECT * FROM items

[Source]

     # File lib/sequel/dataset/sql.rb, line 725
725:     def unordered
726:       order(nil)
727:     end

[Source]

     # File lib/sequel/deprecated.rb, line 125
125:     def upcase_identifiers=(v)
126:       Deprecation.deprecate('Sequel::Dataset#upcase_identifiers=', 'Use Sequel::Dataset#identifier_input_method = :upcase or nil')
127:       @identifier_input_method = v ? :upcase : nil
128:     end

[Source]

     # File lib/sequel/deprecated.rb, line 130
130:     def upcase_identifiers?
131:       Deprecation.deprecate('Sequel::Dataset#upcase_identifiers?', 'Use Sequel::Dataset#identifier_input_method == :upcase')
132:       @identifier_input_method == :upcase
133:     end

Updates values for the dataset. The returned value is generally the number of rows updated, but that is adapter dependent.

[Source]

     # File lib/sequel/dataset.rb, line 253
253:     def update(values={}, opts=(defarg=true;nil))
254:       Deprecation.deprecate("Calling Dataset#update with an argument is deprecated and will raise an error in Sequel 3.0.  Use dataset.clone(opts).update.") unless defarg
255:       execute_dui(defarg ? update_sql(values) : update_sql(value, opts))
256:     end

Formats an UPDATE statement using the given values.

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

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

[Source]

     # File lib/sequel/dataset/sql.rb, line 736
736:     def update_sql(values = {}, opts = (defarg=true;nil))
737:       Deprecation.deprecate("Calling Dataset#update_sql with an argument is deprecated and will raise an error in Sequel 3.0.  Use dataset.clone(opts).update_sql.") unless defarg
738:       opts = opts ? @opts.merge(opts) : @opts
739: 
740:       return static_sql(opts[:sql]) if opts[:sql]
741: 
742:       if opts[:group]
743:         raise InvalidOperation, "A grouped dataset cannot be updated"
744:       elsif (opts[:from].size > 1) or opts[:join]
745:         raise InvalidOperation, "A joined dataset cannot be updated"
746:       end
747:       
748:       sql = "UPDATE #{source_list(@opts[:from])} SET "
749:       set = if values.is_a?(Hash)
750:         values = opts[:defaults].merge(values) if opts[:defaults]
751:         values = values.merge(opts[:overrides]) if opts[:overrides]
752:         # get values from hash
753:         values = transform_save(values) if @transform
754:         values.map do |k, v|
755:           "#{[String, Symbol].any?{|c| k.is_a?(c)} ? quote_identifier(k) : literal(k)} = #{literal(v)}"
756:         end.join(COMMA_SEPARATOR)
757:       else
758:         # copy values verbatim
759:         values
760:       end
761:       sql << set
762:       if where = opts[:where]
763:         sql << " WHERE #{literal(where)}"
764:       end
765: 
766:       sql
767:     end

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

  dataset.group(:a).having(:a).filter(:b) # SELECT * FROM items GROUP BY a HAVING a AND b
  dataset.group(:a).having(:a).where(:b) # SELECT * FROM items WHERE b GROUP BY a HAVING a

[Source]

     # File lib/sequel/dataset/sql.rb, line 773
773:     def where(*cond, &block)
774:       _filter(:where, *cond, &block)
775:     end

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

  dataset.with_sql('SELECT * FROM foo') # SELECT * FROM foo

[Source]

     # File lib/sequel/dataset/sql.rb, line 781
781:     def with_sql(sql, *args)
782:       sql = SQL::PlaceholderLiteralString.new(sql, args) unless args.empty?
783:       clone(:sql=>sql)
784:     end

Protected Instance methods

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

[Source]

     # File lib/sequel/dataset.rb, line 264
264:     def options_overlap(opts)
265:       !(@opts.collect{|k,v| k unless v.nil?}.compact & opts).empty?
266:     end

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

[Source]

     # File lib/sequel/dataset/prepared_statements.rb, line 204
204:     def to_prepared_statement(type, values=nil)
205:       ps = clone
206:       ps.extend(PreparedStatementMethods)
207:       ps.prepared_type = type
208:       ps.prepared_modify_values = values
209:       ps
210:     end

Returns a table reference for use in the FROM clause. Returns an SQL subquery frgament with an optional table alias.

[Source]

     # File lib/sequel/dataset/sql.rb, line 795
795:     def to_table_reference(table_alias=nil)
796:       s = "(#{sql})"
797:       table_alias ? as_sql(s, table_alias) : s
798:     end

[Validate]