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
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 def_mutation_method def_mutation_method delete delete_sql distinct each 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 insert insert_multiple insert_sql inspect intersect interval invert join_clause_sql join_on_clause_sql join_table join_using_clause_sql last limit literal map max min multi_insert multi_insert_sql naked new options_overlap or order order_by order_more ordered_expression_sql paginate placeholder_literal_string_sql prepare prepare print qualified_identifier_sql query 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_overrides single_record single_value sql subscript_sql sum table_exists? to_csv to_hash to_prepared_statement to_table_reference unfiltered union unordered 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)
ARRAY_ACCESS_ERROR_MSG | = | 'You cannot call Dataset#[] with an integer or with no arguments.'.freeze
MAP_ERROR_MSG | = | 'Using Dataset#map with an argument and a block is not allowed'.freeze
GET_ERROR_MSG | = | 'must provide argument or block to Dataset#get, not both'.freeze
IMPORT_ERROR_MSG | = | 'Using Sequel::Dataset#import an empty column array is not allowed'.freeze
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 => [SQL::AliasedExpression.new(LiteralString.new("COUNT(*)").freeze, :count)], :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

### 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

def_mutation_method(*meths)

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

[Source]

         # File lib/sequel/dataset.rb, line 97
     97:     def self.def_mutation_method(*meths)
     98:       meths.each do |meth|
     99:         class_eval("def #{meth}!(*args, &block); mutation_method(:#{meth}, *args, &block) end")
    100:       end
    101:     end

new(db, opts = nil)

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

      DB[:posts]

Sequel::Dataset is an abstract class that is not useful by itself. Each database 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:     end

### Public Instance methods

<<(*args)

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

[Source]

         # File lib/sequel/dataset.rb, line 107
    107:     def <<(*args)
    108:       insert(*args)
    109:     end

[](*conditions)

Returns the first record matching the conditions. Examples:

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

[Source]

        # File lib/sequel/dataset/convenience.rb, line 13
    13:     def [](*conditions)
    14:       raise(Error, ARRAY_ACCESS_ERROR_MSG) if (conditions.length == 1 and conditions.is_a?(Integer)) or conditions.length == 0
    15:       first(*conditions)
    16:     end

[]=(conditions, values)

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 22
    22:     def []=(conditions, values)
    23:       filter(conditions).update(values)
    24:     end

add_graph_aliases(graph_aliases)

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 168
    168:     def add_graph_aliases(graph_aliases)
    169:       ds = select_more(*graph_alias_columns(graph_aliases))
    170:       ds.opts[:graph_aliases] = (ds.opts[:graph_aliases] || {}).merge(graph_aliases)
    171:       ds
    172:     end

aliased_expression_sql(ae)

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

all(&block)

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

[Source]

         # File lib/sequel/dataset.rb, line 120
    120:     def all(&block)
    121:       a = []
    122:       each{|r| a << r}
    123:       post_load(a)
    124:       a.each(&block) if block
    125:       a
    126:     end

and(*cond, &block)

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

      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

array_sql(a)

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

as(aliaz)

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 114
    114:     def as(aliaz)
    115:       ::Sequel::SQL::AliasedExpression.new(self, aliaz)
    116:     end

avg(column)

Returns the average value for the given column.

[Source]

        # File lib/sequel/dataset/convenience.rb, line 27
    27:     def avg(column)
    28:       get{|o| o.avg(column)}
    29:     end

call(type, bind_variables={}, values=nil)

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

case_expression_sql(ce)

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

cast_sql(expr, type)

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.cast_type_literal(type)})"
    53:     end

clone(opts = {})

Returns a new clone of the dataset with with the given options merged. If the options changed include options in COLUMN_CHANGE_OPTS, the cached columns are deleted.

[Source]

         # File lib/sequel/dataset.rb, line 131
    131:     def clone(opts = {})
    132:       c = super()
    133:       c.opts = @opts.merge(opts)
    134:       c.instance_variable_set(:@columns, nil) if opts.keys.any?{|o| COLUMN_CHANGE_OPTS.include?(o)}
    135:       c
    136:     end

column_all_sql(ca)

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

columns()

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 147
    147:     def columns
    148:       return @columns if @columns
    149:       ds = unfiltered.unordered.clone(:distinct => nil, :limit => 1)
    150:       ds.each{break}
    151:       @columns = ds.instance_variable_get(:@columns)
    152:       @columns || []
    153:     end

columns!()

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

[Source]

         # File lib/sequel/dataset.rb, line 157
    157:     def columns!
    158:       @columns = nil
    159:       columns
    160:     end

complex_expression_sql(op, args)

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

count()

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

def_mutation_method(*meths)

Add a mutation method to this dataset instance.

[Source]

         # File lib/sequel/dataset.rb, line 163
    163:     def def_mutation_method(*meths)
    164:       meths.each do |meth|
    165:         instance_eval("def #{meth}!(*args, &block); mutation_method(:#{meth}, *args, &block) end")
    166:       end
    167:     end

delete()

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 171
    171:     def delete
    172:       execute_dui(delete_sql)
    173:     end

delete_sql()

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
     91:       opts = @opts
     92:
     93:       return static_sql(opts[:sql]) if opts[:sql]
     94:
     95:       if opts[:group]
     96:         raise InvalidOperation, "Grouped datasets cannot be deleted from"
     97:       elsif opts[:from].is_a?(Array) && opts[:from].size > 1
     98:         raise InvalidOperation, "Joined datasets cannot be deleted from"
     99:       end
    100:
    101:       sql = "DELETE FROM #{source_list(opts[:from])}"
    102:
    103:       if where = opts[:where]
    104:         sql << " WHERE #{literal(where)}"
    105:       end
    106:
    107:       sql
    108:     end

distinct(*args)

Returns a copy of the dataset with the SQL DISTINCT clause. The DISTINCT clause is used to remove duplicate rows from the output. If arguments are provided, uses a DISTINCT ON clause, in which case it will only be distinct on those columns, instead of all returned columns.

     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 118
    118:     def distinct(*args)
    119:       clone(:distinct => args)
    120:     end

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

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 177
    177:     def each(&block)
    178:       if @opts[:graph]
    179:         graph_each(&block)
    180:       else
    181:         if row_proc = @row_proc
    182:           fetch_rows(select_sql){|r| yield row_proc.call(r)}
    183:         else
    184:           fetch_rows(select_sql, &block)
    185:         end
    186:       end
    187:       self
    188:     end

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

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

[Source]

        # File lib/sequel/extensions/pagination.rb, line 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

empty?()

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

[Source]

        # File lib/sequel/dataset/convenience.rb, line 32
    32:     def empty?
    33:       get(1).nil?
    34:     end

except(dataset, all = false)

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 127
    127:     def except(dataset, all = false)
    128:       compound_clone(:except, dataset, all)
    129:     end

exclude(*cond, &block)

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 135
    135:     def exclude(*cond, &block)
    136:       clause = (@opts[:having] ? :having : :where)
    137:       cond = cond.first if cond.size == 1
    138:       cond = filter_expr(cond, &block)
    139:       cond = SQL::BooleanExpression.invert(cond)
    140:       cond = SQL::BooleanExpression.new(:AND, @opts[clause], cond) if @opts[clause]
    141:       clone(clause => cond)
    142:     end

exists()

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 148
    148:     def exists
    149:       LiteralString.new("EXISTS (#{select_sql})")
    150:     end

fetch_rows(sql, &block)

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 192
    192:     def fetch_rows(sql, &block)
    193:       raise NotImplementedError, NOTIMPL_MSG
    194:     end

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

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

[Source]

         # File lib/sequel/adapters/do.rb, line 180
    180:       def fetch_rows(sql)
    181:         execute(sql) do |reader|
    182:           cols = @columns = reader.fields.map{|f| output_identifier(f)}
    183:           while(reader.next!) do
    184:             h = {}
    185:             cols.zip(reader.values).each{|k, v| h[k] = v}
    186:             yield h
    187:           end
    188:         end
    189:         self
    190:       end

fetch_rows(sql, &block)

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

[Source]

         # File lib/sequel/adapters/jdbc.rb, line 430
    430:       def fetch_rows(sql, &block)
    431:         execute(sql){|result| process_result_set(result, &block)}
    432:         self
    433:       end

filter(*cond, &block)

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

filter accepts the following argument types:

- Hash - list of equality/inclusion expressions
- Array - depends:
  - If first member is a string, assumes the rest of the arguments are parameters and interpolates them into the string.
  - If all members are arrays of length two, treats the same way as a hash, except it allows for duplicate keys to be specified.
- 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 199
    199:     def filter(*cond, &block)
    200:       _filter(@opts[:having] ? :having : :where, *cond, &block)
    201:     end

first(*args, &block)

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

      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 55
    55:     def first(*args, &block)
    56:       ds = block ? filter(&block) : self
    57:
    58:       if args.empty?
    59:         ds.single_record
    60:       else
    61:         args = (args.size == 1) ? args.first : args
    62:         if Integer === args
    63:           ds.limit(args).all
    64:         else
    65:           ds.filter(args).single_record
    66:         end
    67:       end
    68:     end

first_source()

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 205
    205:     def first_source
    206:       source = @opts[:from]
    207:       if source.nil? || source.empty?
    208:         raise Error, 'No source specified for query'
    209:       end
    210:       case s = source.first
    211:       when Hash
    212:         s.values.first
    213:       when Symbol
    214:         sch, table, aliaz = split_symbol(s)
    215:         aliaz ? aliaz.to_sym : s
    216:       else
    217:         s
    218:       end
    219:     end

from(*source)

Returns a copy of the dataset with the source changed.

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

[Source]

         # File lib/sequel/dataset/sql.rb, line 226
    226:     def from(*source)
    227:       clone(:from=>source.empty? ? nil : source)
    228:     end

from_self()

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 235
    235:     def from_self
    236:       fs = {}
    237:       @opts.keys.each{|k| fs[k] = nil}
    238:       fs[:from] = [self]
    239:       clone(fs)
    240:     end

function_sql(f)

SQL fragment specifying an SQL function call

[Source]

         # File lib/sequel/dataset/sql.rb, line 243
    243:     def function_sql(f)
    244:       args = f.args
    245:       "#{f.f}#{args.empty? ? '()' : literal(args)}"
    246:     end

get(column=nil, &block)

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

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

[Source]

        # File lib/sequel/dataset/convenience.rb, line 75
    75:     def get(column=nil, &block)
    76:       if column
    77:         raise(Error, GET_ERROR_MSG) if block
    78:         select(column).single_value
    79:       else
    80:         select(&block).single_value
    81:       end
    82:     end

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

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

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

      # CREATE TABLE artists (id INTEGER, name TEXT);
      # CREATE TABLE albums (id INTEGER, name TEXT, artist_id INTEGER);
      DB[:artists].left_outer_join(:albums, :artist_id=>:id).first
      => {:id=>albums.id, :name=>albums.name, :artist_id=>albums.artist_id}
      DB[:artists].graph(:albums, :artist_id=>:id).first
      => {:artists=>{:id=>artists.id, :name=>artists.name}, :albums=>{:id=>albums.id, :name=>albums.name, :artist_id=>albums.artist_id}}

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

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

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

Arguments:

- dataset - Can be a symbol (specifying a table), another dataset, or an object that responds to .dataset and 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 47
     47:     def graph(dataset, join_conditions = nil, options = {}, &block)
     48:       # Allow the use of a model, dataset, or symbol as the first argument
     49:       # Find the table name/dataset based on the argument
     50:       dataset = dataset.dataset if dataset.respond_to?(:dataset)
     51:       case dataset
     52:       when Symbol
     53:         table = dataset
     54:         dataset = @db[dataset]
     55:       when ::Sequel::Dataset
     56:         table = dataset.first_source
     57:       else
     58:         raise Error, "The dataset argument should be a symbol, dataset, or model"
     59:       end
     60:
     61:       # Raise Sequel::Error with explanation that the table alias has been used
     62:       raise_alias_error = lambda do
     63:         raise(Error, "this #{options[:table_alias] ? 'alias' : 'table'} has already been been used, please specify " \
     64:           "#{options[:table_alias] ? 'a different alias' : 'an alias via the :table_alias option'}")
     65:       end
     66:
     67:       # Only allow table aliases that haven't been used
     68:       table_alias = options[:table_alias] || table
     69:       raise_alias_error.call if @opts[:graph] && @opts[:graph][:table_aliases] && @opts[:graph][:table_aliases].include?(table_alias)
     70:
     71:       # Join the table early in order to avoid cloning the dataset twice
     72:       ds = join_table(options[:join_type] || :left_outer, table, join_conditions, :table_alias=>table_alias, :implicit_qualifier=>options[:implicit_qualifier], &block)
     73:       opts = ds.opts
     74:
     75:       # Whether to include the table in the result set
     76:       add_table = options[:select] == false ? false : true
     77:       # Whether to add the columns to the list of column aliases
     78:       add_columns = !ds.opts.include?(:graph_aliases)
     79:
     80:       # Setup the initial graph data structure if it doesn't exist
     81:       unless graph = opts[:graph]
     82:         master = ds.first_source
     83:         raise_alias_error.call if master == table_alias
     84:         # Master hash storing all .graph related information
     85:         graph = opts[:graph] = {}
     86:         # Associates column aliases back to tables and columns
     87:         column_aliases = graph[:column_aliases] = {}
     88:         # Associates table alias (the master is never aliased)
     89:         table_aliases = graph[:table_aliases] = {master=>self}
     90:         # Keep track of the alias numbers used
     91:         ca_num = graph[:column_alias_num] = Hash.new(0)
     92:         # All columns in the master table are never
     93:         # aliased, but are not included if set_graph_aliases
     94:         # has been used.
     95:         if add_columns
     96:           select = opts[:select] = []
     97:           columns.each do |column|
     98:             column_aliases[column] = [master, column]
     99:             select.push(SQL::QualifiedIdentifier.new(master, column))
    100:           end
    101:         end
    102:       end
    103:
    104:       # Add the table alias to the list of aliases
    105:       # Even if it isn't been used in the result set,
    106:       # we add a key for it with a nil value so we can check if it
    107:       # is used more than once
    108:       table_aliases = graph[:table_aliases]
    109:       table_aliases[table_alias] = add_table ? dataset : nil
    110:
    111:       # Add the columns to the selection unless we are ignoring them
    112:       if add_table && add_columns
    113:         select = opts[:select]
    114:         column_aliases = graph[:column_aliases]
    115:         ca_num = graph[:column_alias_num]
    116:         # Which columns to add to the result set
    117:         cols = options[:select] || dataset.columns
    118:         # If the column hasn't been used yet, don't alias it.
    119:         # If it has been used, try table_column.
    120:         # If that has been used, try table_column_N
    121:         # using the next value of N that we know hasn't been
    122:         # used
    123:         cols.each do |column|
    124:           col_alias, identifier = if column_aliases[column]
    125:             column_alias = "#{table_alias}_#{column}""#{table_alias}_#{column}"
    126:             if column_aliases[column_alias]
    127:               column_alias_num = ca_num[column_alias]
    128:               column_alias = "#{column_alias}_#{column_alias_num}""#{column_alias}_#{column_alias_num}"
    129:               ca_num[column_alias] += 1
    130:             end
    131:             [column_alias, SQL::QualifiedIdentifier.new(table_alias, column).as(column_alias)]
    132:           else
    133:             [column, SQL::QualifiedIdentifier.new(table_alias, column)]
    134:           end
    135:           column_aliases[col_alias] = [table_alias, column]
    136:           select.push(identifier)
    137:         end
    138:       end
    139:       ds
    140:     end

grep(cols, terms)

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 256
    256:     def grep(cols, terms)
    257:       filter(SQL::BooleanExpression.new(:OR, *Array(cols).collect{|c| SQL::StringExpression.like(c, *terms)}))
    258:     end

group(*columns)

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 265
    265:     def group(*columns)
    266:       clone(:group => columns)
    267:     end

group_and_count(*columns)

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 89
    89:     def group_and_count(*columns)
    90:       group(*columns).select(*(columns + [COUNT_OF_ALL_AS_COUNT])).order(:count)
    91:     end

group_by(*columns)

Alias for group

having(*cond, &block)

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 274
    274:     def having(*cond, &block)
    275:       raise(InvalidOperation, "Can only specify a HAVING clause on a grouped dataset") unless @opts[:group]
    276:       _filter(:having, *cond, &block)
    277:     end

import(columns, values, opts={})

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 111
    111:     def import(columns, values, opts={})
    112:       return @db.transaction{execute_dui("INSERT INTO #{quote_schema_table(@opts[:from].first)} (#{identifier_list(columns)}) VALUES #{literal(values)}")} if values.is_a?(Dataset)
    113:
    114:       return if values.empty?
    115:       raise(Error, IMPORT_ERROR_MSG) if columns.empty?
    116:
    117:       if slice_size = opts[:commit_every] || opts[:slice]
    118:         offset = 0
    119:         loop do
    120:           @db.transaction(opts){multi_insert_sql(columns, values[offset, slice_size]).each{|st| execute_dui(st)}}
    121:           offset += slice_size
    122:           break if offset >= values.length
    123:         end
    124:       else
    125:         statements = multi_insert_sql(columns, values)
    126:         @db.transaction{statements.each{|st| execute_dui(st)}}
    127:       end
    128:     end

insert(*values)

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 198
    198:     def insert(*values)
    199:       execute_insert(insert_sql(*values))
    200:     end

insert_multiple(array, &block)

Inserts multiple values. If a block is given it is invoked for each item in the given array before inserting it. See multi_insert as a possible faster version that inserts multiple records in one SQL statement.

[Source]

         # File lib/sequel/dataset/sql.rb, line 283
    283:     def insert_multiple(array, &block)
    284:       if block
    285:         array.each {|i| insert(block[i])}
    286:       else
    287:         array.each {|i| insert(i)}
    288:       end
    289:     end

insert_sql(*values)

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 299
    299:     def insert_sql(*values)
    300:       return static_sql(@opts[:sql]) if @opts[:sql]
    301:
    302:       from = source_list(@opts[:from])
    303:       case values.size
    304:       when 0
    305:         values = {}
    306:       when 1
    307:         vals = values.at(0)
    308:         if [Hash, Dataset, Array].any?{|c| vals.is_a?(c)}
    309:           values = vals
    310:         elsif vals.respond_to?(:values)
    311:           values = vals.values
    312:         end
    313:       end
    314:
    315:       case values
    316:       when Array
    317:         if values.empty?
    318:           insert_default_values_sql
    319:         else
    320:           "INSERT INTO #{from} VALUES #{literal(values)}"
    321:         end
    322:       when Hash
    323:         values = @opts[:defaults].merge(values) if @opts[:defaults]
    324:         values = values.merge(@opts[:overrides]) if @opts[:overrides]
    325:         if values.empty?
    326:           insert_default_values_sql
    327:         else
    328:           fl, vl = [], []
    329:           values.each do |k, v|
    330:             fl << literal(String === k ? k.to_sym : k)
    331:             vl << literal(v)
    332:           end
    333:           "INSERT INTO #{from} (#{fl.join(COMMA_SEPARATOR)}) VALUES (#{vl.join(COMMA_SEPARATOR)})"
    334:         end
    335:       when Dataset
    336:         "INSERT INTO #{from} #{literal(values)}"
    337:       end
    338:     end

inspect()

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

[Source]

         # File lib/sequel/dataset.rb, line 204
    204:     def inspect
    205:       "#<#{self.class}: #{sql.inspect}>"
    206:     end

intersect(dataset, all = false)

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 345
    345:     def intersect(dataset, all = false)
    346:       compound_clone(:intersect, dataset, all)
    347:     end

interval(column)

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

[Source]

         # File lib/sequel/dataset/convenience.rb, line 132
    132:     def interval(column)
    133:       get{|o| o.max(column) - o.min(column)}
    134:     end

invert()

Inverts the current filter

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

[Source]

         # File lib/sequel/dataset/sql.rb, line 353
    353:     def invert
    354:       having, where = @opts[:having], @opts[:where]
    355:       raise(Error, "No current filter") unless having || where
    356:       o = {}
    357:       o[:having] = SQL::BooleanExpression.invert(having) if having
    358:       o[:where] = SQL::BooleanExpression.invert(where) if where
    359:       clone(o)
    360:     end

join_clause_sql(jc)

SQL fragment specifying a JOIN clause without ON or USING.

[Source]

         # File lib/sequel/dataset/sql.rb, line 363
    363:     def join_clause_sql(jc)
    364:       table = jc.table
    365:       table_alias = jc.table_alias
    366:       table_alias = nil if table == table_alias
    367:       tref = table_ref(table)
    368:       " #{join_type_sql(jc.join_type)} #{table_alias ? as_sql(tref, table_alias) : tref}"
    369:     end

join_on_clause_sql(jc)

SQL fragment specifying a JOIN clause with ON.

[Source]

         # File lib/sequel/dataset/sql.rb, line 372
    372:     def join_on_clause_sql(jc)
    373:       "#{join_clause_sql(jc)} ON #{literal(filter_expr(jc.on))}"
    374:     end

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

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 411
    411:     def join_table(type, table, expr=nil, options={}, &block)
    412:       if [Symbol, String].any?{|c| options.is_a?(c)}
    413:         table_alias = options
    414:         last_alias = nil
    415:       else
    416:         table_alias = options[:table_alias]
    417:         last_alias = options[:implicit_qualifier]
    418:       end
    419:       if Dataset === table
    420:         if table_alias.nil?
    421:           table_alias_num = (@opts[:num_dataset_sources] || 0) + 1
    422:           table_alias = "t#{table_alias_num}"
    423:         end
    424:         table_name = table_alias
    425:       else
    426:         table = table.table_name if table.respond_to?(:table_name)
    427:         table_name = table_alias || table
    428:       end
    429:
    430:       join = if expr.nil? and !block_given?
    431:         SQL::JoinClause.new(type, table, table_alias)
    432:       elsif Array === expr and !expr.empty? and expr.all?{|x| Symbol === x}
    433:         raise(Sequel::Error, "can't use a block if providing an array of symbols as expr") if block_given?
    434:         SQL::JoinUsingClause.new(expr, type, table, table_alias)
    435:       else
    436:         last_alias ||= @opts[:last_joined_table] || (first_source.is_a?(Dataset) ? 't1' : first_source)
    437:         if Sequel.condition_specifier?(expr)
    438:           expr = expr.collect do |k, v|
    439:             k = qualified_column_name(k, table_name) if k.is_a?(Symbol)
    440:             v = qualified_column_name(v, last_alias) if v.is_a?(Symbol)
    441:             [k,v]
    442:           end
    443:         end
    444:         if block_given?
    445:           expr2 = yield(table_name, last_alias, @opts[:join] || [])
    446:           expr = expr ? SQL::BooleanExpression.new(:AND, expr, expr2) : expr2
    447:         end
    448:         SQL::JoinOnClause.new(expr, type, table, table_alias)
    449:       end
    450:
    451:       opts = {:join => (@opts[:join] || []) + [join], :last_joined_table => table_name}
    452:       opts[:num_dataset_sources] = table_alias_num if table_alias_num
    453:       clone(opts)
    454:     end

join_using_clause_sql(jc)

SQL fragment specifying a JOIN clause with USING.

[Source]

         # File lib/sequel/dataset/sql.rb, line 377
    377:     def join_using_clause_sql(jc)
    378:       "#{join_clause_sql(jc)} USING (#{column_list(jc.using)})"
    379:     end

last(*args, &block)

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 140
    140:     def last(*args, &block)
    141:       raise(Error, 'No order specified') unless @opts[:order]
    142:       reverse.first(*args, &block)
    143:     end

limit(l, o = nil)

If given an integer, the dataset will contain only the first l results. If given a range, it will contain only those at offsets within that range. If a second argument is given, it is used as an offset.

      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 462
    462:     def limit(l, o = nil)
    463:       return from_self.limit(l, o) if @opts[:sql]
    464:
    465:       if Range === l
    466:         o = l.first
    467:         l = l.last - l.first + (l.exclude_end? ? 0 : 1)
    468:       end
    469:       l = l.to_i
    470:       raise(Error, 'Limits must be greater than or equal to 1') unless l >= 1
    471:       opts = {:limit => l}
    472:       if o
    473:         o = o.to_i
    474:         raise(Error, 'Offsets must be greater than or equal to 0') unless o >= 0
    475:         opts[:offset] = o
    476:       end
    477:       clone(opts)
    478:     end

literal(v)

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 490
    490:     def literal(v)
    491:       case v
    492:       when String
    493:         return v if v.is_a?(LiteralString)
    494:         v.is_a?(SQL::Blob) ? literal_blob(v) : literal_string(v)
    495:       when Symbol
    496:         literal_symbol(v)
    497:       when Integer
    498:         literal_integer(v)
    499:       when Hash
    500:         literal_hash(v)
    501:       when SQL::Expression
    502:         literal_expression(v)
    503:       when Float
    504:         literal_float(v)
    505:       when BigDecimal
    506:         literal_big_decimal(v)
    507:       when NilClass
    508:         NULL
    509:       when TrueClass
    510:         literal_true
    511:       when FalseClass
    512:         literal_false
    513:       when Array
    514:         literal_array(v)
    515:       when Time
    516:         literal_time(v)
    517:       when DateTime
    518:         literal_datetime(v)
    519:       when Date
    520:         literal_date(v)
    521:       when Dataset
    522:         literal_dataset(v)
    523:       else
    524:         literal_other(v)
    525:       end
    526:     end

map(column=nil, &block)

Maps column values for each record in the dataset (if a column name is given), or performs the stock mapping functionality of Enumerable. 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 151
    151:     def map(column=nil, &block)
    152:       if column
    153:         raise(Error, MAP_ERROR_MSG) if block
    154:         super(){|r| r[column]}
    155:       else
    156:         super(&block)
    157:       end
    158:     end

max(column)

Returns the maximum value for the given column.

[Source]

         # File lib/sequel/dataset/convenience.rb, line 161
    161:     def max(column)
    162:       get{|o| o.max(column)}
    163:     end

min(column)

Returns the minimum value for the given column.

[Source]

         # File lib/sequel/dataset/convenience.rb, line 166
    166:     def min(column)
    167:       get{|o| o.min(column)}
    168:     end

multi_insert(hashes, opts={})

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

      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 180
    180:     def multi_insert(hashes, opts={})
    181:       return if hashes.empty?
    182:       columns = hashes.first.keys
    183:       import(columns, hashes.map{|h| columns.map{|c| h[c]}}, opts)
    184:     end

multi_insert_sql(columns, values)

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

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

[Source]

         # File lib/sequel/dataset/sql.rb, line 534
    534:     def multi_insert_sql(columns, values)
    535:       s = "INSERT INTO #{source_list(@opts[:from])} (#{identifier_list(columns)}) VALUES "
    536:       values.map{|r| s + literal(r)}
    537:     end

naked()

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 210
    210:     def naked
    211:       ds = clone
    212:       ds.row_proc = nil
    213:       ds
    214:     end

or(*cond, &block)

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 543
    543:     def or(*cond, &block)
    544:       clause = (@opts[:having] ? :having : :where)
    545:       raise(InvalidOperation, "No existing filter found.") unless @opts[clause]
    546:       cond = cond.first if cond.size == 1
    547:       clone(clause => SQL::BooleanExpression.new(:OR, @opts[clause], filter_expr(cond, &block)))
    548:     end

order(*columns, &block)

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 563
    563:     def order(*columns, &block)
    564:       columns += Array(virtual_row_block_call(block)) if block
    565:       clone(:order => (columns.compact.empty?) ? nil : columns)
    566:     end

order_by(*columns, &block)

Alias for order

order_more(*columns, &block)

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 574
    574:     def order_more(*columns, &block)
    575:       order(*Array(@opts[:order]).concat(columns), &block)
    576:     end

ordered_expression_sql(oe)

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

[Source]

         # File lib/sequel/dataset/sql.rb, line 580
    580:     def ordered_expression_sql(oe)
    581:       "#{literal(oe.expression)} #{oe.descending ? 'DESC' : 'ASC'}"
    582:     end

paginate(page_no, page_size, record_count=nil)

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

[Source]

        # File lib/sequel/extensions/pagination.rb, line 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

placeholder_literal_string_sql(pls)

SQL fragment for a literal string with placeholders

[Source]

         # File lib/sequel/dataset/sql.rb, line 585
    585:     def placeholder_literal_string_sql(pls)
    586:       args = pls.args.dup
    587:       s = pls.str.gsub(QUESTION_MARK){literal(args.shift)}
    588:       s = "(#{s})" if pls.parens
    589:       s
    590:     end

prepare(type, name=nil, values=nil)

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

prepare(type, name=nil, values=nil)

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

[Source]

         # File lib/sequel/adapters/jdbc.rb, line 437
    437:       def prepare(type, name=nil, values=nil)
    438:         ps = to_prepared_statement(type, values)
    439:         ps.extend(PreparedStatementMethods)
    440:         if name
    441:           ps.prepared_statement_name = name
    442:           db.prepared_statements[name] = ps
    443:         end
    444:         ps
    445:       end

print(*cols)

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

qualified_identifier_sql(qcr)

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

[Source]

         # File lib/sequel/dataset/sql.rb, line 594
    594:     def qualified_identifier_sql(qcr)
    595:       [qcr.table, qcr.column].map{|x| [SQL::QualifiedIdentifier, SQL::Identifier, Symbol].any?{|c| x.is_a?(c)} ? literal(x) : quote_identifier(x)}.join('.')
    596:     end

query(&block)

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

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

Which is the same as:

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

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

[Source]

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

quote_identifier(name)

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

[Source]

         # File lib/sequel/dataset/sql.rb, line 601
    601:     def quote_identifier(name)
    602:       return name if name.is_a?(LiteralString)
    603:       name = name.value if name.is_a?(SQL::Identifier)
    604:       name = input_identifier(name)
    605:       name = quoted_identifier(name) if quote_identifiers?
    606:       name
    607:     end

quote_identifiers?()

Whether this dataset quotes identifiers.

[Source]

         # File lib/sequel/dataset.rb, line 217
    217:     def quote_identifiers?
    218:       @quote_identifiers
    219:     end

quote_schema_table(table)

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

[Source]

         # File lib/sequel/dataset/sql.rb, line 611
    611:     def quote_schema_table(table)
    612:       schema, table = schema_and_table(table)
    613:       "#{"#{quote_identifier(schema)}." if schema}#{quote_identifier(table)}"
    614:     end

quoted_identifier(name)

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

[Source]

         # File lib/sequel/dataset/sql.rb, line 619
    619:     def quoted_identifier(name)
    620:       "\"#{name.to_s.gsub('"', '""')}\""
    621:     end

range(column)

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

[Source]

         # File lib/sequel/dataset/convenience.rb, line 188
    188:     def range(column)
    189:       if r = select{|o| [o.min(column).as(:v1), o.max(column).as(:v2)]}.first
    190:         (r[:v1]..r[:v2])
    191:       end
    192:     end

reverse(*order)

Alias for reverse_order

reverse_order(*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 625
    625:     def reverse_order(*order)
    626:       order(*invert_order(order.empty? ? @opts[:order] : order))
    627:     end

schema_and_table(table_name)

Split the schema information from the table

[Source]

         # File lib/sequel/dataset/sql.rb, line 631
    631:     def schema_and_table(table_name)
    632:       sch = db.default_schema if db
    633:       case table_name
    634:       when Symbol
    635:         s, t, a = split_symbol(table_name)
    636:         [s||sch, t]
    637:       when SQL::QualifiedIdentifier
    638:         [table_name.table, table_name.column]
    639:       when SQL::Identifier
    640:         [sch, table_name.value]
    641:       when String
    642:         [sch, table_name]
    643:       else
    644:         raise Error, 'table_name should be a Symbol, SQL::QualifiedIdentifier, SQL::Identifier, or String'
    645:       end
    646:     end

select(*columns, &block)

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

      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 655
    655:     def select(*columns, &block)
    656:       columns += Array(virtual_row_block_call(block)) if block
    657:       clone(:select => columns)
    658:     end

select_all()

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 663
    663:     def select_all
    664:       clone(:select => nil)
    665:     end

select_more(*columns, &block)

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 672
    672:     def select_more(*columns, &block)
    673:       select(*Array(@opts[:select]).concat(columns), &block)
    674:     end

select_sql()

Formats a SELECT statement

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

[Source]

         # File lib/sequel/dataset/sql.rb, line 679
    679:     def select_sql
    680:       return static_sql(@opts[:sql]) if @opts[:sql]
    681:       sql = 'SELECT'
    682:       select_clause_order.each{|x| send("select_#{x}_sql""select_#{x}_sql", sql)}
    683:       sql
    684:     end

server(servr)

Set the server for this dataset to use. Used to pick a specific database shard to run a query against, or to override the default (which is SELECT uses :read_only database and all other queries use the :default database).

[Source]

         # File lib/sequel/dataset.rb, line 224
    224:     def server(servr)
    225:       clone(:server=>servr)
    226:     end

set(*args)

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

[Source]

         # File lib/sequel/dataset.rb, line 230
    230:     def set(*args)
    231:       update(*args)
    232:     end

set_defaults(hash)

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 236
    236:     def set_defaults(hash)
    237:       clone(:defaults=>(@opts[:defaults]||{}).merge(hash))
    238:     end

set_graph_aliases(graph_aliases)

This allows you to manually specify the graph aliases to use when using graph. You can use it to only select certain columns, and have those columns mapped to specific aliases in the result set. This is the equivalent of .select for a graphed dataset, and must be used instead of .select whenever graphing is used. 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 159
    159:     def set_graph_aliases(graph_aliases)
    160:       ds = select(*graph_alias_columns(graph_aliases))
    161:       ds.opts[:graph_aliases] = graph_aliases
    162:       ds
    163:     end

set_overrides(hash)

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

[Source]

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

single_record()

Returns the first record in the dataset.

[Source]

         # File lib/sequel/dataset/convenience.rb, line 195
    195:     def single_record
    196:       clone(:limit=>1).each{|r| return r}
    197:       nil
    198:     end

single_value()

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 202
    202:     def single_value
    203:       if r = naked.clone(:graph=>false).single_record
    204:         r.values.first
    205:       end
    206:     end

sql()

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

[Source]

         # File lib/sequel/dataset/sql.rb, line 687
    687:     def sql
    688:       select_sql
    689:     end

subscript_sql(s)

SQL fragment for specifying subscripts (SQL arrays)

[Source]

         # File lib/sequel/dataset/sql.rb, line 692
    692:     def subscript_sql(s)
    693:       "#{literal(s.f)}[#{s.sub.join(COMMA_SEPARATOR)}]"
    694:     end

sum(column)

Returns the sum for the given column.

[Source]

         # File lib/sequel/dataset/convenience.rb, line 209
    209:     def sum(column)
    210:       get{|o| o.sum(column)}
    211:     end

table_exists?()

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 216
    216:     def table_exists?
    217:       raise(Sequel::Error, "this dataset has fixed SQL") if @opts[:sql]
    218:       raise(Sequel::Error, "this dataset selects from multiple sources") if @opts[:from].size != 1
    219:       t = @opts[:from].first
    220:       raise(Sequel::Error, "this dataset selects from a sub query") if t.is_a?(Dataset)
    221:       @db.table_exists?(t)
    222:     end

to_csv(include_column_titles = true)

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

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

[Source]

         # File lib/sequel/dataset/convenience.rb, line 232
    232:     def to_csv(include_column_titles = true)
    233:       n = naked
    234:       cols = n.columns
    235:       csv = ''
    236:       csv << "#{cols.join(COMMA_SEPARATOR)}\r\n" if include_column_titles
    237:       n.each{|r| csv << "#{cols.collect{|c| r[c]}.join(COMMA_SEPARATOR)}\r\n"}
    238:       csv
    239:     end

to_hash(key_column, value_column = nil)

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

[Source]

         # File lib/sequel/dataset/convenience.rb, line 245
    245:     def to_hash(key_column, value_column = nil)
    246:       inject({}) do |m, r|
    247:         m[r[key_column]] = value_column ? r[value_column] : r
    248:         m
    249:       end
    250:     end

unfiltered()

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 699
    699:     def unfiltered
    700:       clone(:where => nil, :having => nil)
    701:     end

union(dataset, all = false)

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 708
    708:     def union(dataset, all = false)
    709:       compound_clone(:union, dataset, all)
    710:     end

unordered()

Returns a copy of the dataset with no order.

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

[Source]

         # File lib/sequel/dataset/sql.rb, line 715
    715:     def unordered
    716:       order(nil)
    717:     end

update(values={})

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 248
    248:     def update(values={})
    249:       execute_dui(update_sql(values))
    250:     end

update_sql(values = {})

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 726
    726:     def update_sql(values = {})
    727:       opts = @opts
    728:
    729:       return static_sql(opts[:sql]) if opts[:sql]
    730:
    731:       if opts[:group]
    732:         raise InvalidOperation, "A grouped dataset cannot be updated"
    733:       elsif (opts[:from].size > 1) or opts[:join]
    734:         raise InvalidOperation, "A joined dataset cannot be updated"
    735:       end
    736:
    737:       sql = "UPDATE #{source_list(@opts[:from])} SET "
    738:       set = if values.is_a?(Hash)
    739:         values = opts[:defaults].merge(values) if opts[:defaults]
    740:         values = values.merge(opts[:overrides]) if opts[:overrides]
    741:         # get values from hash
    742:         values.map do |k, v|
    743:           "#{[String, Symbol].any?{|c| k.is_a?(c)} ? quote_identifier(k) : literal(k)} = #{literal(v)}"
    744:         end.join(COMMA_SEPARATOR)
    745:       else
    746:         # copy values verbatim
    747:         values
    748:       end
    749:       sql << set
    750:       if where = opts[:where]
    751:         sql << " WHERE #{literal(where)}"
    752:       end
    753:
    754:       sql
    755:     end

where(*cond, &block)

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 761
    761:     def where(*cond, &block)
    762:       _filter(:where, *cond, &block)
    763:     end

with_sql(sql, *args)

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

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

[Source]

         # File lib/sequel/dataset/sql.rb, line 769
    769:     def with_sql(sql, *args)
    770:       sql = SQL::PlaceholderLiteralString.new(sql, args) unless args.empty?
    771:       clone(:sql=>sql)
    772:     end

### Protected Instance methods

options_overlap(opts)

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

[Source]

         # File lib/sequel/dataset.rb, line 258
    258:     def options_overlap(opts)
    259:       !(@opts.collect{|k,v| k unless v.nil?}.compact & opts).empty?
    260:     end

to_prepared_statement(type, values=nil)

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

[Source]

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

to_table_reference(table_alias=nil)

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 783
    783:     def to_table_reference(table_alias=nil)
    784:       s = "(#{sql})"
    785:       table_alias ? as_sql(s, table_alias) : s
    786:     end

[Validate]