Class | Sequel::Dataset

In:

lib/sequel/adapters/do.rb
lib/sequel/adapters/jdbc.rb
lib/sequel/adapters/utils/stored_procedures.rb
lib/sequel/dataset.rb
lib/sequel/dataset/convenience.rb
lib/sequel/dataset/graph.rb
lib/sequel/dataset/prepared_statements.rb
lib/sequel/dataset/sql.rb
lib/sequel/dataset/actions.rb
lib/sequel/dataset/features.rb
lib/sequel/dataset/query.rb
lib/sequel/extensions/pagination.rb
lib/sequel/extensions/pretty_table.rb
lib/sequel/extensions/query.rb

Parent: | Sequel::Dataset

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

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

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

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

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

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

### Methods

<< [] []= _insert_sql _update_sql add_graph_aliases aliased_expression_sql all and array_sql as avg bind call case_expression_sql cast_sql clause_methods clone column_all_sql columns columns! complex_expression_sql compound_from_self constant_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 first_source_alias 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 new options_overlap or order order_by order_more ordered_expression_sql paginate placeholder_literal_string_sql prepare prepare print qualified_identifier_sql qualify qualify_to qualify_to_first_source query quote_identifier quote_identifiers? quote_schema_table quoted_identifier range requires_sql_standard_datetimes? reverse reverse_order schema_and_table select select_all select_more select_sql server set set_defaults set_graph_aliases set_overrides simple_select_all? single_record single_value sql subscript_sql sum supports_cte? supports_distinct_on? supports_intersect_except? supports_intersect_except_all? supports_is_true? supports_join_using? supports_multiple_column_in? supports_timestamp_timezones? supports_timestamp_usecs? supports_window_functions? to_csv to_hash to_prepared_statement truncate truncate_sql unfiltered ungraphed ungrouped union unlimited unordered update update_sql where window_function_sql window_sql with with_recursive 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::StoredProcedureMethods
Module Sequel::Dataset::StoredProcedures
Module Sequel::Dataset::UnnumberedArgumentMapper

### 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 except exclude filter from from_self full_outer_join graph group group_and_count group_by having inner_join intersect invert join join_table left_outer_join limit naked or order order_by order_more paginate qualify query reverse reverse_order right_outer_join select select_all select_more server set_defaults set_graph_aliases set_overrides unfiltered ungraphed ungrouped union unlimited unordered where with with_recursive with_sql'.collect{|x| x.to_sym}

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

NON_SQL_OPTIONS | = | [:server, :defaults, :overrides] |  | Which options don‘t affect the SQL generation. Used by simple_select_all? to determine if this is a simple SELECT * FROM table.
NOTIMPL_MSG | = | "This method must be overridden in Sequel adapters".freeze
WITH_SUPPORTED | = | :select_with_sql
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
CONDITIONED_JOIN_TYPES | = | [:inner, :full_outer, :right_outer, :left_outer, :full, :right, :left] |  | These symbols have _join methods created (e.g. inner_join) that call join_table with the symbol, passing along the arguments and block from the method call.
UNCONDITIONED_JOIN_TYPES | = | [:natural, :natural_left, :natural_right, :natural_full, :cross] |  | These symbols have _join methods created (e.g. natural_join) that call join_table with the symbol. They only accept a single table argument which is passed to join_table, and they raise an error if called with a block.
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]
DATASET_ALIAS_BASE_NAME | = | 't'.freeze
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
QUALIFY_KEYS | = | [:select, :where, :having, :order, :group]
QUESTION_MARK | = | '?'.freeze
DELETE_CLAUSE_METHODS | = | clause_methods(:delete, %w'from where')
INSERT_CLAUSE_METHODS | = | clause_methods(:insert, %w'into columns values')
SELECT_CLAUSE_METHODS | = | clause_methods(:select, %w'with distinct columns from join where group having compounds order limit')
UPDATE_CLAUSE_METHODS | = | clause_methods(:update, %w'table set where')
TIMESTAMP_FORMAT | = | "'%Y-%m-%d %H:%M:%S%N%z'".freeze
STANDARD_TIMESTAMP_FORMAT | = | "TIMESTAMP #{TIMESTAMP_FORMAT}".freeze
TWO_ARITY_OPERATORS | = | ::Sequel::SQL::ComplexExpression::TWO_ARITY_OPERATORS
WILDCARD | = | '*'.freeze
SQL_WITH | = | "WITH ".freeze
FROM_SELF_KEEP_OPTS | = | [:graph, :eager_graph, :graph_aliases]

### External Aliases

inner_join | -> | join

### Attributes

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

clause_methods(type, clauses)

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

[Source]

       # File lib/sequel/dataset/sql.rb, line 6
    6:     def self.clause_methods(type, clauses)
    7:       clauses.map{|clause| "#{type}_#{clause}_sql""#{type}_#{clause}_sql"}.freeze
    8:     end

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 91
    91:     def self.def_mutation_method(*meths)
    92:       meths.each do |meth|
    93:         class_eval("def #{meth}!(*args, &block); mutation_method(:#{meth}, *args, &block) end", __FILE__, __LINE__)
    94:       end
    95:     end

new(db, opts={})

Use the convert_types default setting from the database

[Source]

         # File lib/sequel/adapters/jdbc.rb, line 455
    455:       def initialize(db, opts={})
    456:         @convert_types = db.convert_types
    457:         super
    458:       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 77
    77:     def initialize(db, opts = nil)
    78:       @db = db
    79:       @quote_identifiers = db.quote_identifiers? if db.respond_to?(:quote_identifiers?)
    80:       @identifier_input_method = db.identifier_input_method if db.respond_to?(:identifier_input_method)
    81:       @identifier_output_method = db.identifier_output_method if db.respond_to?(:identifier_output_method)
    82:       @opts = opts || {}
    83:       @row_proc = nil
    84:     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/actions.rb, line 6
    6:     def <<(*args)
    7:       insert(*args)
    8:     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.first.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 given 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 6
     6:     def add_graph_aliases(graph_aliases)
     7:       ds = select_more(*graph_alias_columns(graph_aliases))
     8:       ds.opts[:graph_aliases] = (ds.opts[:graph_aliases] || ds.opts[:graph][:column_aliases] || {}).merge(graph_aliases)
     9:       ds
    10:     end

aliased_expression_sql(ae)

SQL fragment for the aliased expression

[Source]

        # File lib/sequel/dataset/sql.rb, line 46
    46:     def aliased_expression_sql(ae)
    47:       as_sql(literal(ae.expression), ae.aliaz)
    48:     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/actions.rb, line 12
    12:     def all(&block)
    13:       a = []
    14:       each{|r| a << r}
    15:       post_load(a)
    16:       a.each(&block) if block
    17:       a
    18:     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/query.rb, line 11
    11:     def and(*cond, &block)
    12:       raise(InvalidOperation, "No existing filter found.") unless @opts[:having] || @opts[:where]
    13:       filter(*cond, &block)
    14:     end

array_sql(a)

SQL fragment for the SQL array.

[Source]

        # File lib/sequel/dataset/sql.rb, line 51
    51:     def array_sql(a)
    52:       a.empty? ? '(NULL)' : "(#{expression_list(a)})"
    53:     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 102
    102:     def as(aliaz)
    103:       ::Sequel::SQL::AliasedExpression.new(self, aliaz)
    104:     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:       aggregate_dataset.get{avg(column)}
    29:     end

bind(bind_vars={})

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

[Source]

         # File lib/sequel/dataset/prepared_statements.rb, line 173
    173:     def bind(bind_vars={})
    174:       clone(:bind_vars=>@opts[:bind_vars] ? @opts[:bind_vars].merge(bind_vars) : bind_vars)
    175:     end

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

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 182
    182:     def call(type, bind_variables={}, *values, &block)
    183:       prepare(type, nil, *values).call(bind_variables, &block)
    184:     end

case_expression_sql(ce)

SQL fragment for specifying given CaseExpression.

[Source]

        # File lib/sequel/dataset/sql.rb, line 56
    56:     def case_expression_sql(ce)
    57:       sql = '(CASE '
    58:       sql << "#{literal(ce.expression)} " if ce.expression
    59:       ce.conditions.collect{ |c,r|
    60:         sql << "WHEN #{literal(c)} THEN #{literal(r)} "
    61:       }
    62:       sql << "ELSE #{literal(ce.default)} END)"
    63:     end

cast_sql(expr, type)

SQL fragment for the SQL CAST expression.

[Source]

        # File lib/sequel/dataset/sql.rb, line 66
    66:     def cast_sql(expr, type)
    67:       "CAST(#{literal(expr)} AS #{db.cast_type_literal(type)})"
    68:     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 109
    109:     def clone(opts = {})
    110:       c = super()
    111:       c.opts = @opts.merge(opts)
    112:       c.instance_variable_set(:@columns, nil) if opts.keys.any?{|o| COLUMN_CHANGE_OPTS.include?(o)}
    113:       c
    114:     end

column_all_sql(ca)

SQL fragment for specifying all columns in a given table.

[Source]

        # File lib/sequel/dataset/sql.rb, line 71
    71:     def column_all_sql(ca)
    72:       "#{quote_schema_table(ca.table)}.*"
    73:     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/actions.rb, line 29
    29:     def columns
    30:       return @columns if @columns
    31:       ds = unfiltered.unordered.clone(:distinct => nil, :limit => 1)
    32:       ds.each{break}
    33:       @columns = ds.instance_variable_get(:@columns)
    34:       @columns || []
    35:     end

columns!()

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

[Source]

        # File lib/sequel/dataset/actions.rb, line 39
    39:     def columns!
    40:       @columns = nil
    41:       columns
    42:     end

complex_expression_sql(op, args)

SQL fragment for complex expressions

[Source]

         # File lib/sequel/dataset/sql.rb, line 76
     76:     def complex_expression_sql(op, args)
     77:       case op
     78:       when *IS_OPERATORS
     79:         r = args.at(1)
     80:         if r.nil? || supports_is_true?
     81:           raise(InvalidOperation, 'Invalid argument used for IS operator') unless v = IS_LITERALS[r]
     82:           "(#{literal(args.at(0))} #{op} #{v})"
     83:         elsif op == :IS
     84:           complex_expression_sql("=""=", args)
     85:         else
     86:           complex_expression_sql(:OR, [SQL::BooleanExpression.new("!=""!=", *args), SQL::BooleanExpression.new(:IS, args.at(0), nil)])
     87:         end
     88:       when :IN, "NOT IN""NOT IN"
     89:         cols = args.at(0)
     90:         if !supports_multiple_column_in? && cols.is_a?(Array)
     91:           expr = SQL::BooleanExpression.new(:OR, *args.at(1).to_a.map{|vals| SQL::BooleanExpression.from_value_pairs(cols.zip(vals).map{|col, val| [col, val]})})
     92:           literal(op == :IN ? expr : ~expr)
     93:         else
     94:           "(#{literal(cols)} #{op} #{literal(args.at(1))})"
     95:         end
     96:       when *TWO_ARITY_OPERATORS
     97:         "(#{literal(args.at(0))} #{op} #{literal(args.at(1))})"
     98:       when *N_ARITY_OPERATORS
     99:         "(#{args.collect{|a| literal(a)}.join(" #{op} ")})"
    100:       when :NOT
    101:         "NOT #{literal(args.at(0))}"
    102:       when :NOOP
    103:         literal(args.at(0))
    104:       when 'B~''B~'
    105:         "~#{literal(args.at(0))}"
    106:       else
    107:         raise(InvalidOperation, "invalid operator #{op}")
    108:       end
    109:     end

constant_sql(constant)

SQL fragment for constants

[Source]

         # File lib/sequel/dataset/sql.rb, line 112
    112:     def constant_sql(constant)
    113:       constant.to_s
    114:     end

count()

Returns the number of records in the dataset.

[Source]

         # File lib/sequel/dataset/sql.rb, line 117
    117:     def count
    118:       aggregate_dataset.get{COUNT(:*){}.as(count)}.to_i
    119:     end

def_mutation_method(*meths)

Add a mutation method to this dataset instance.

[Source]

         # File lib/sequel/dataset.rb, line 117
    117:     def def_mutation_method(*meths)
    118:       meths.each do |meth|
    119:         instance_eval("def #{meth}!(*args, &block); mutation_method(:#{meth}, *args, &block) end", __FILE__, __LINE__)
    120:       end
    121:     end

delete()

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

[Source]

        # File lib/sequel/dataset/actions.rb, line 46
    46:     def delete
    47:       execute_dui(delete_sql)
    48:     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 125
    125:     def delete_sql
    126:       return static_sql(opts[:sql]) if opts[:sql]
    127:       check_modification_allowed!
    128:       clause_sql(:delete)
    129:     end

distinct(*args)

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

     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/query.rb, line 25
    25:     def distinct(*args)
    26:       raise(InvalidOperation, "DISTINCT ON not supported") if !args.empty? && !supports_distinct_on?
    27:       clone(:distinct => args)
    28:     end

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

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

Note that this method is not safe to use on many adapters if you are running additional queries inside the provided block. If you are running queries inside the block, you use should all instead of each.

[Source]

        # File lib/sequel/dataset/actions.rb, line 56
    56:     def each(&block)
    57:       if @opts[:graph]
    58:         graph_each(&block)
    59:       else
    60:         if row_proc = @row_proc
    61:           fetch_rows(select_sql){|r| yield row_proc.call(r)}
    62:         else
    63:           fetch_rows(select_sql, &block)
    64:         end
    65:       end
    66:       self
    67:     end

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

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

[Source]

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

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, opts={})

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

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

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

[Source]

        # File lib/sequel/dataset/query.rb, line 40
    40:     def except(dataset, opts={})
    41:       opts = {:all=>opts} unless opts.is_a?(Hash)
    42:       raise(InvalidOperation, "EXCEPT not supported") unless supports_intersect_except?
    43:       raise(InvalidOperation, "EXCEPT ALL not supported") if opts[:all] && !supports_intersect_except_all?
    44:       compound_clone(:except, dataset, opts)
    45:     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/query.rb, line 51
    51:     def exclude(*cond, &block)
    52:       clause = (@opts[:having] ? :having : :where)
    53:       cond = cond.first if cond.size == 1
    54:       cond = filter_expr(cond, &block)
    55:       cond = SQL::BooleanExpression.invert(cond)
    56:       cond = SQL::BooleanExpression.new(:AND, @opts[clause], cond) if @opts[clause]
    57:       clone(clause => cond)
    58:     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 135
    135:     def exists
    136:       LiteralString.new("EXISTS (#{select_sql})")
    137:     end

fetch_rows(sql, &block)

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

[Source]

         # File lib/sequel/adapters/jdbc.rb, line 461
    461:       def fetch_rows(sql, &block)
    462:         execute(sql){|result| process_result_set(result, &block)}
    463:         self
    464:       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/actions.rb, line 71
    71:     def fetch_rows(sql, &block)
    72:       raise NotImplementedError, NOTIMPL_MSG
    73:     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 182
    182:       def fetch_rows(sql)
    183:         execute(sql) do |reader|
    184:           cols = @columns = reader.fields.map{|f| output_identifier(f)}
    185:           while(reader.next!) do
    186:             h = {}
    187:             cols.zip(reader.values).each{|k, v| h[k] = v}
    188:             yield h
    189:           end
    190:         end
    191:         self
    192:       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_filtering.rdoc for more examples and details.

[Source]

         # File lib/sequel/dataset/query.rb, line 107
    107:     def filter(*cond, &block)
    108:       _filter(@opts[:having] ? :having : :where, *cond, &block)
    109:     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()

Alias for first_source_alias

first_source_alias()

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

[Source]

         # File lib/sequel/dataset/sql.rb, line 141
    141:     def first_source_alias
    142:       source = @opts[:from]
    143:       if source.nil? || source.empty?
    144:         raise Error, 'No source specified for query'
    145:       end
    146:       case s = source.first
    147:       when SQL::AliasedExpression
    148:         s.aliaz
    149:       when Symbol
    150:         sch, table, aliaz = split_symbol(s)
    151:         aliaz ? aliaz.to_sym : s
    152:       else
    153:         s
    154:       end
    155:     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/query.rb, line 116
    116:     def from(*source)
    117:       table_alias_num = 0
    118:       sources = []
    119:       source.each do |s|
    120:         case s
    121:         when Hash
    122:           s.each{|k,v| sources << SQL::AliasedExpression.new(k,v)}
    123:         when Dataset
    124:           sources << SQL::AliasedExpression.new(s, dataset_alias(table_alias_num+=1))
    125:         when Symbol
    126:           sch, table, aliaz = split_symbol(s)
    127:           if aliaz
    128:             s = sch ? SQL::QualifiedIdentifier.new(sch.to_sym, table.to_sym) : SQL::Identifier.new(table.to_sym)
    129:             sources << SQL::AliasedExpression.new(s, aliaz.to_sym)
    130:           else
    131:             sources << s
    132:           end
    133:         else
    134:           sources << s
    135:         end
    136:       end
    137:       o = {:from=>sources.empty? ? nil : sources}
    138:       o[:num_dataset_sources] = table_alias_num if table_alias_num > 0
    139:       clone(o)
    140:     end

from_self(opts={})

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

      ds = DB[:items].order(:name).select(:id, :name)
      ds.sql                         #=> "SELECT id,name FROM items ORDER BY name"
      ds.from_self.sql               #=> "SELECT * FROM (SELECT id, name FROM items ORDER BY name) AS 't1'"
      ds.from_self(:alias=>:foo).sql #=> "SELECT * FROM (SELECT id, name FROM items ORDER BY name) AS 'foo'"

[Source]

         # File lib/sequel/dataset/query.rb, line 149
    149:     def from_self(opts={})
    150:       fs = {}
    151:       @opts.keys.each{|k| fs[k] = nil unless FROM_SELF_KEEP_OPTS.include?(k)}
    152:       clone(fs).from(opts[:alias] ? as(opts[:alias]) : self)
    153:     end

function_sql(f)

SQL fragment specifying an SQL function call

[Source]

         # File lib/sequel/dataset/sql.rb, line 159
    159:     def function_sql(f)
    160:       args = f.args
    161:       "#{f.f}#{args.empty? ? '()' : literal(args)}"
    162:     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:
  - :from_self_alias - The alias to use when the receiver is not a graphed dataset but it contains multiple FROM tables or a JOIN. In this case, the receiver is wrapped in a from_self before graphing, and this option determines the alias to use.
  - :implicit_qualifier - The qualifier of implicit conditions, see join_table.
  - :join_type - The type of join to use (passed to join_table). Defaults to :left_outer.
  - :select - An array of columns to select. When not used, selects all columns in the given dataset. When set to false, selects no columns and is like simply joining the tables, though graph keeps some metadata about 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 60
     60:     def graph(dataset, join_conditions = nil, options = {}, &block)
     61:       # Allow the use of a model, dataset, or symbol as the first argument
     62:       # Find the table name/dataset based on the argument
     63:       dataset = dataset.dataset if dataset.respond_to?(:dataset)
     64:       table_alias = options[:table_alias]
     65:       case dataset
     66:       when Symbol
     67:         table = dataset
     68:         dataset = @db[dataset]
     69:         table_alias ||= table
     70:       when ::Sequel::Dataset
     71:         if dataset.simple_select_all?
     72:           table = dataset.opts[:from].first
     73:           table_alias ||= table
     74:         else
     75:           table = dataset
     76:           table_alias ||= dataset_alias((@opts[:num_dataset_sources] || 0)+1)
     77:         end
     78:       else
     79:         raise Error, "The dataset argument should be a symbol, dataset, or model"
     80:       end
     81:
     82:       # Raise Sequel::Error with explanation that the table alias has been used
     83:       raise_alias_error = lambda do
     84:         raise(Error, "this #{options[:table_alias] ? 'alias' : 'table'} has already been been used, please specify " \
     85:           "#{options[:table_alias] ? 'a different alias' : 'an alias via the :table_alias option'}")
     86:       end
     87:
     88:       # Only allow table aliases that haven't been used
     89:       raise_alias_error.call if @opts[:graph] && @opts[:graph][:table_aliases] && @opts[:graph][:table_aliases].include?(table_alias)
     90:
     91:       # Use a from_self if this is already a joined table
     92:       ds = (!@opts[:graph] && (@opts[:from].length > 1 || @opts[:join])) ? from_self(:alias=>options[:from_self_alias] || first_source) : self
     93:
     94:       # Join the table early in order to avoid cloning the dataset twice
     95:       ds = ds.join_table(options[:join_type] || :left_outer, table, join_conditions, :table_alias=>table_alias, :implicit_qualifier=>options[:implicit_qualifier], &block)
     96:       opts = ds.opts
     97:
     98:       # Whether to include the table in the result set
     99:       add_table = options[:select] == false ? false : true
    100:       # Whether to add the columns to the list of column aliases
    101:       add_columns = !ds.opts.include?(:graph_aliases)
    102:
    103:       # Setup the initial graph data structure if it doesn't exist
    104:       unless graph = opts[:graph]
    105:         master = ds.first_source_alias
    106:         raise_alias_error.call if master == table_alias
    107:         # Master hash storing all .graph related information
    108:         graph = opts[:graph] = {}
    109:         # Associates column aliases back to tables and columns
    110:         column_aliases = graph[:column_aliases] = {}
    111:         # Associates table alias (the master is never aliased)
    112:         table_aliases = graph[:table_aliases] = {master=>self}
    113:         # Keep track of the alias numbers used
    114:         ca_num = graph[:column_alias_num] = Hash.new(0)
    115:         # All columns in the master table are never
    116:         # aliased, but are not included if set_graph_aliases
    117:         # has been used.
    118:         if add_columns
    119:           select = opts[:select] = []
    120:           columns.each do |column|
    121:             column_aliases[column] = [master, column]
    122:             select.push(SQL::QualifiedIdentifier.new(master, column))
    123:           end
    124:         end
    125:       end
    126:
    127:       # Add the table alias to the list of aliases
    128:       # Even if it isn't been used in the result set,
    129:       # we add a key for it with a nil value so we can check if it
    130:       # is used more than once
    131:       table_aliases = graph[:table_aliases]
    132:       table_aliases[table_alias] = add_table ? dataset : nil
    133:
    134:       # Add the columns to the selection unless we are ignoring them
    135:       if add_table && add_columns
    136:         select = opts[:select]
    137:         column_aliases = graph[:column_aliases]
    138:         ca_num = graph[:column_alias_num]
    139:         # Which columns to add to the result set
    140:         cols = options[:select] || dataset.columns
    141:         # If the column hasn't been used yet, don't alias it.
    142:         # If it has been used, try table_column.
    143:         # If that has been used, try table_column_N
    144:         # using the next value of N that we know hasn't been
    145:         # used
    146:         cols.each do |column|
    147:           col_alias, identifier = if column_aliases[column]
    148:             column_alias = "#{table_alias}_#{column}""#{table_alias}_#{column}"
    149:             if column_aliases[column_alias]
    150:               column_alias_num = ca_num[column_alias]
    151:               column_alias = "#{column_alias}_#{column_alias_num}""#{column_alias}_#{column_alias_num}"
    152:               ca_num[column_alias] += 1
    153:             end
    154:             [column_alias, SQL::QualifiedIdentifier.new(table_alias, column).as(column_alias)]
    155:           else
    156:             [column, SQL::QualifiedIdentifier.new(table_alias, column)]
    157:           end
    158:           column_aliases[col_alias] = [table_alias, column]
    159:           select.push(identifier)
    160:         end
    161:       end
    162:       ds
    163:     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/query.rb, line 163
    163:     def grep(cols, terms)
    164:       filter(SQL::BooleanExpression.new(:OR, *Array(cols).collect{|c| SQL::StringExpression.like(c, *terms)}))
    165:     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/query.rb, line 172
    172:     def group(*columns)
    173:       clone(:group => (columns.compact.empty? ? nil : columns))
    174:     end

group_and_count(*columns)

Returns a dataset grouped by the given column with count by group, order by the count of records (in ascending order). Column aliases may be supplied, and will be included in the select clause.

Examples:

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

[Source]

        # File lib/sequel/dataset/convenience.rb, line 93
    93:     def group_and_count(*columns)
    94:       groups = columns.map do |c|
    95:         c_table, column, _ = split_symbol(c)
    96:         c_table ? column.to_sym.qualify(c_table) : column.to_sym
    97:       end
    98:       group(*groups).select(*(columns + [COUNT_OF_ALL_AS_COUNT])).order(:count)
    99:     end

group_by(*columns)

Alias for group

having(*cond, &block)

Returns a copy of the dataset with the HAVING conditions changed. 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/query.rb, line 180
    180:     def having(*cond, &block)
    181:       _filter(:having, *cond, &block)
    182:     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 119
    119:     def import(columns, values, opts={})
    120:       return @db.transaction{insert(columns, values)} if values.is_a?(Dataset)
    121:
    122:       return if values.empty?
    123:       raise(Error, IMPORT_ERROR_MSG) if columns.empty?
    124:
    125:       if slice_size = opts[:commit_every] || opts[:slice]
    126:         offset = 0
    127:         loop do
    128:           @db.transaction(opts){multi_insert_sql(columns, values[offset, slice_size]).each{|st| execute_dui(st)}}
    129:           offset += slice_size
    130:           break if offset >= values.length
    131:         end
    132:       else
    133:         statements = multi_insert_sql(columns, values)
    134:         @db.transaction{statements.each{|st| execute_dui(st)}}
    135:       end
    136:     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. See insert_sql.

[Source]

        # File lib/sequel/dataset/actions.rb, line 78
    78:     def insert(*values)
    79:       execute_insert(insert_sql(*values))
    80:     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 168
    168:     def insert_multiple(array, &block)
    169:       if block
    170:         array.each {|i| insert(block[i])}
    171:       else
    172:         array.each {|i| insert(i)}
    173:       end
    174:     end

insert_sql(*values)

Formats an INSERT statement using the given values. The API is a little complex, and best explained by example:

      # Default values
      DB[:items].insert_sql #=> 'INSERT INTO items DEFAULT VALUES'
      DB[:items].insert_sql({}) #=> 'INSERT INTO items DEFAULT VALUES'
      # Values without columns
      DB[:items].insert_sql(1,2,3) #=> 'INSERT INTO items VALUES (1, 2, 3)'
      DB[:items].insert_sql([1,2,3]) #=> 'INSERT INTO items VALUES (1, 2, 3)'
      # Values with columns
      DB[:items].insert_sql([:a, :b], [1,2]) #=> 'INSERT INTO items (a, b) VALUES (1, 2)'
      DB[:items].insert_sql(:a => 1, :b => 2) #=> 'INSERT INTO items (a, b) VALUES (1, 2)'
      # Using a subselect
      DB[:items].insert_sql(DB[:old_items]) #=> 'INSERT INTO items SELECT * FROM old_items
      # Using a subselect with columns
      DB[:items].insert_sql([:a, :b], DB[:old_items]) #=> 'INSERT INTO items (a, b) SELECT * FROM old_items

[Source]

         # File lib/sequel/dataset/sql.rb, line 192
    192:     def insert_sql(*values)
    193:       return static_sql(@opts[:sql]) if @opts[:sql]
    194:
    195:       check_modification_allowed!
    196:
    197:       columns = []
    198:
    199:       case values.size
    200:       when 0
    201:         return insert_sql({})
    202:       when 1
    203:         case vals = values.at(0)
    204:         when Hash
    205:           vals = @opts[:defaults].merge(vals) if @opts[:defaults]
    206:           vals = vals.merge(@opts[:overrides]) if @opts[:overrides]
    207:           values = []
    208:           vals.each do |k,v|
    209:             columns << k
    210:             values << v
    211:           end
    212:         when Dataset, Array, LiteralString
    213:           values = vals
    214:         else
    215:           if vals.respond_to?(:values) && (v = vals.values).is_a?(Hash)
    216:             return insert_sql(v)
    217:           end
    218:         end
    219:       when 2
    220:         if (v0 = values.at(0)).is_a?(Array) && ((v1 = values.at(1)).is_a?(Array) || v1.is_a?(Dataset) || v1.is_a?(LiteralString))
    221:           columns, values = v0, v1
    222:           raise(Error, "Different number of values and columns given to insert_sql") if values.is_a?(Array) and columns.length != values.length
    223:         end
    224:       end
    225:
    226:       columns = columns.map{|k| literal(String === k ? k.to_sym : k)}
    227:       clone(:columns=>columns, :values=>values)._insert_sql
    228:     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 125
    125:     def inspect
    126:       "#<#{self.class}: #{sql.inspect}>"
    127:     end

intersect(dataset, opts={})

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

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

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

[Source]

         # File lib/sequel/dataset/query.rb, line 194
    194:     def intersect(dataset, opts={})
    195:       opts = {:all=>opts} unless opts.is_a?(Hash)
    196:       raise(InvalidOperation, "INTERSECT not supported") unless supports_intersect_except?
    197:       raise(InvalidOperation, "INTERSECT ALL not supported") if opts[:all] && !supports_intersect_except_all?
    198:       compound_clone(:intersect, dataset, opts)
    199:     end

interval(column)

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

[Source]

         # File lib/sequel/dataset/convenience.rb, line 140
    140:     def interval(column)
    141:       aggregate_dataset.get{max(column) - min(column)}
    142:     end

invert()

Inverts the current filter

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

[Source]

         # File lib/sequel/dataset/query.rb, line 205
    205:     def invert
    206:       having, where = @opts[:having], @opts[:where]
    207:       raise(Error, "No current filter") unless having || where
    208:       o = {}
    209:       o[:having] = SQL::BooleanExpression.invert(having) if having
    210:       o[:where] = SQL::BooleanExpression.invert(where) if where
    211:       clone(o)
    212:     end

join_clause_sql(jc)

SQL fragment specifying a JOIN clause without ON or USING.

[Source]

         # File lib/sequel/dataset/sql.rb, line 231
    231:     def join_clause_sql(jc)
    232:       table = jc.table
    233:       table_alias = jc.table_alias
    234:       table_alias = nil if table == table_alias
    235:       tref = table_ref(table)
    236:       " #{join_type_sql(jc.join_type)} #{table_alias ? as_sql(tref, table_alias) : tref}"
    237:     end

join_on_clause_sql(jc)

SQL fragment specifying a JOIN clause with ON.

[Source]

         # File lib/sequel/dataset/sql.rb, line 240
    240:     def join_on_clause_sql(jc)
    241:       "#{join_clause_sql(jc)} ON #{literal(filter_expr(jc.on))}"
    242:     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_qualifier - The name to use for qualifying implicit conditions. By default, the last joined or primary table is used.
- block - The block argument should only be given if a JOIN with an ON clause is used, in which case it yields the table alias/name for the table currently being joined, the table alias/name for the last joined (or first table), and an array of previous SQL::JoinClause.

[Source]

         # File lib/sequel/dataset/sql.rb, line 279
    279:     def join_table(type, table, expr=nil, options={}, &block)
    280:       using_join = expr.is_a?(Array) && !expr.empty? && expr.all?{|x| x.is_a?(Symbol)}
    281:       if using_join && !supports_join_using?
    282:         h = {}
    283:         expr.each{|s| h[s] = s}
    284:         return join_table(type, table, h, options)
    285:       end
    286:
    287:       if [Symbol, String].any?{|c| options.is_a?(c)}
    288:         table_alias = options
    289:         last_alias = nil
    290:       else
    291:         table_alias = options[:table_alias]
    292:         last_alias = options[:implicit_qualifier]
    293:       end
    294:       if Dataset === table
    295:         if table_alias.nil?
    296:           table_alias_num = (@opts[:num_dataset_sources] || 0) + 1
    297:           table_alias = dataset_alias(table_alias_num)
    298:         end
    299:         table_name = table_alias
    300:       else
    301:         table = table.table_name if table.respond_to?(:table_name)
    302:         table_name = table_alias || table
    303:       end
    304:
    305:       join = if expr.nil? and !block_given?
    306:         SQL::JoinClause.new(type, table, table_alias)
    307:       elsif using_join
    308:         raise(Sequel::Error, "can't use a block if providing an array of symbols as expr") if block_given?
    309:         SQL::JoinUsingClause.new(expr, type, table, table_alias)
    310:       else
    311:         last_alias ||= @opts[:last_joined_table] || first_source_alias
    312:         if Sequel.condition_specifier?(expr)
    313:           expr = expr.collect do |k, v|
    314:             k = qualified_column_name(k, table_name) if k.is_a?(Symbol)
    315:             v = qualified_column_name(v, last_alias) if v.is_a?(Symbol)
    316:             [k,v]
    317:           end
    318:         end
    319:         if block_given?
    320:           expr2 = yield(table_name, last_alias, @opts[:join] || [])
    321:           expr = expr ? SQL::BooleanExpression.new(:AND, expr, expr2) : expr2
    322:         end
    323:         SQL::JoinOnClause.new(expr, type, table, table_alias)
    324:       end
    325:
    326:       opts = {:join => (@opts[:join] || []) + [join], :last_joined_table => table_name}
    327:       opts[:num_dataset_sources] = table_alias_num if table_alias_num
    328:       clone(opts)
    329:     end

join_using_clause_sql(jc)

SQL fragment specifying a JOIN clause with USING.

[Source]

         # File lib/sequel/dataset/sql.rb, line 245
    245:     def join_using_clause_sql(jc)
    246:       "#{join_clause_sql(jc)} USING (#{column_list(jc.using)})"
    247:     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 148
    148:     def last(*args, &block)
    149:       raise(Error, 'No order specified') unless @opts[:order]
    150:       reverse.first(*args, &block)
    151:     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/query.rb, line 220
    220:     def limit(l, o = nil)
    221:       return from_self.limit(l, o) if @opts[:sql]
    222:
    223:       if Range === l
    224:         o = l.first
    225:         l = l.last - l.first + (l.exclude_end? ? 0 : 1)
    226:       end
    227:       l = l.to_i
    228:       raise(Error, 'Limits must be greater than or equal to 1') unless l >= 1
    229:       opts = {:limit => l}
    230:       if o
    231:         o = o.to_i
    232:         raise(Error, 'Offsets must be greater than or equal to 0') unless o >= 0
    233:         opts[:offset] = o
    234:       end
    235:       clone(opts)
    236:     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 341
    341:     def literal(v)
    342:       case v
    343:       when String
    344:         return v if v.is_a?(LiteralString)
    345:         v.is_a?(SQL::Blob) ? literal_blob(v) : literal_string(v)
    346:       when Symbol
    347:         literal_symbol(v)
    348:       when Integer
    349:         literal_integer(v)
    350:       when Hash
    351:         literal_hash(v)
    352:       when SQL::Expression
    353:         literal_expression(v)
    354:       when Float
    355:         literal_float(v)
    356:       when BigDecimal
    357:         literal_big_decimal(v)
    358:       when NilClass
    359:         NULL
    360:       when TrueClass
    361:         literal_true
    362:       when FalseClass
    363:         literal_false
    364:       when Array
    365:         literal_array(v)
    366:       when Time
    367:         literal_time(v)
    368:       when DateTime
    369:         literal_datetime(v)
    370:       when Date
    371:         literal_date(v)
    372:       when Dataset
    373:         literal_dataset(v)
    374:       else
    375:         literal_other(v)
    376:       end
    377:     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 159
    159:     def map(column=nil, &block)
    160:       if column
    161:         raise(Error, MAP_ERROR_MSG) if block
    162:         super(){|r| r[column]}
    163:       else
    164:         super(&block)
    165:       end
    166:     end

max(column)

Returns the maximum value for the given column.

[Source]

         # File lib/sequel/dataset/convenience.rb, line 169
    169:     def max(column)
    170:       aggregate_dataset.get{max(column)}
    171:     end

min(column)

Returns the minimum value for the given column.

[Source]

         # File lib/sequel/dataset/convenience.rb, line 174
    174:     def min(column)
    175:       aggregate_dataset.get{min(column)}
    176:     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 188
    188:     def multi_insert(hashes, opts={})
    189:       return if hashes.empty?
    190:       columns = hashes.first.keys
    191:       import(columns, hashes.map{|h| columns.map{|c| h[c]}}, opts)
    192:     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 385
    385:     def multi_insert_sql(columns, values)
    386:       values.map{|r| insert_sql(columns, r)}
    387:     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 131
    131:     def naked
    132:       ds = clone
    133:       ds.row_proc = nil
    134:       ds
    135:     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/query.rb, line 242
    242:     def or(*cond, &block)
    243:       clause = (@opts[:having] ? :having : :where)
    244:       raise(InvalidOperation, "No existing filter found.") unless @opts[clause]
    245:       cond = cond.first if cond.size == 1
    246:       clone(clause => SQL::BooleanExpression.new(:OR, @opts[clause], filter_expr(cond, &block)))
    247:     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/query.rb, line 262
    262:     def order(*columns, &block)
    263:       columns += Array(Sequel.virtual_row(&block)) if block
    264:       clone(:order => (columns.compact.empty?) ? nil : columns)
    265:     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/query.rb, line 273
    273:     def order_more(*columns, &block)
    274:       columns = @opts[:order] + columns if @opts[:order]
    275:       order(*columns, &block)
    276:     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 391
    391:     def ordered_expression_sql(oe)
    392:       "#{literal(oe.expression)} #{oe.descending ? 'DESC' : 'ASC'}"
    393:     end

paginate(page_no, page_size, record_count=nil)

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

[Source]

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

placeholder_literal_string_sql(pls)

SQL fragment for a literal string with placeholders

[Source]

         # File lib/sequel/dataset/sql.rb, line 396
    396:     def placeholder_literal_string_sql(pls)
    397:       args = pls.args
    398:       s = if args.is_a?(Hash)
    399:         re = /:(#{args.keys.map{|k| Regexp.escape(k.to_s)}.join('|')})\b/
    400:         pls.str.gsub(re){literal(args[$1.to_sym])}
    401:       else
    402:         i = -1
    403:         pls.str.gsub(QUESTION_MARK){literal(args.at(i+=1))}
    404:       end
    405:       s = "(#{s})" if pls.parens
    406:       s
    407:     end

prepare(type, name=nil, *values)

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 195
    195:     def prepare(type, name=nil, *values)
    196:       ps = to_prepared_statement(type, values)
    197:       db.prepared_statements[name] = ps if name
    198:       ps
    199:     end

prepare(type, name=nil, *values)

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

[Source]

         # File lib/sequel/adapters/jdbc.rb, line 468
    468:       def prepare(type, name=nil, *values)
    469:         ps = to_prepared_statement(type, values)
    470:         ps.extend(PreparedStatementMethods)
    471:         if name
    472:           ps.prepared_statement_name = name
    473:           db.prepared_statements[name] = ps
    474:         end
    475:         ps
    476:       end

print(*cols)

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

[Source]

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

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 411
    411:     def qualified_identifier_sql(qcr)
    412:       [qcr.table, qcr.column].map{|x| [SQL::QualifiedIdentifier, SQL::Identifier, Symbol].any?{|c| x.is_a?(c)} ? literal(x) : quote_identifier(x)}.join('.')
    413:     end

qualify(table=first_source)

Qualify to the given table, or first source if not table is given.

[Source]

         # File lib/sequel/dataset/sql.rb, line 416
    416:     def qualify(table=first_source)
    417:       qualify_to(table)
    418:     end

qualify_to(table)

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

[Source]

         # File lib/sequel/dataset/sql.rb, line 424
    424:     def qualify_to(table)
    425:       o = @opts
    426:       return clone if o[:sql]
    427:       h = {}
    428:       (o.keys & QUALIFY_KEYS).each do |k|
    429:         h[k] = qualified_expression(o[k], table)
    430:       end
    431:       h[:select] = [SQL::ColumnAll.new(table)] if !o[:select] || o[:select].empty?
    432:       clone(h)
    433:     end

qualify_to_first_source()

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

[Source]

         # File lib/sequel/dataset/sql.rb, line 440
    440:     def qualify_to_first_source
    441:       qualify_to(first_source)
    442:     end

query(&block)

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

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

Which is the same as:

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

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

[Source]

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

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 447
    447:     def quote_identifier(name)
    448:       return name if name.is_a?(LiteralString)
    449:       name = name.value if name.is_a?(SQL::Identifier)
    450:       name = input_identifier(name)
    451:       name = quoted_identifier(name) if quote_identifiers?
    452:       name
    453:     end

quote_identifiers?()

Whether this dataset quotes identifiers.

[Source]

       # File lib/sequel/dataset/features.rb, line 4
    4:     def quote_identifiers?
    5:       @quote_identifiers
    6:     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 457
    457:     def quote_schema_table(table)
    458:       schema, table = schema_and_table(table)
    459:       "#{"#{quote_identifier(schema)}." if schema}#{quote_identifier(table)}"
    460:     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 465
    465:     def quoted_identifier(name)
    466:       "\"#{name.to_s.gsub('"', '""')}\""
    467:     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 196
    196:     def range(column)
    197:       if r = aggregate_dataset.select{[min(column).as(v1), max(column).as(v2)]}.first
    198:         (r[:v1]..r[:v2])
    199:       end
    200:     end

requires_sql_standard_datetimes?()

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

[Source]

        # File lib/sequel/dataset/features.rb, line 10
    10:     def requires_sql_standard_datetimes?
    11:       false
    12:     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/query.rb, line 280
    280:     def reverse_order(*order)
    281:       order(*invert_order(order.empty? ? @opts[:order] : order))
    282:     end

schema_and_table(table_name)

Split the schema information from the table

[Source]

         # File lib/sequel/dataset/sql.rb, line 470
    470:     def schema_and_table(table_name)
    471:       sch = db.default_schema if db
    472:       case table_name
    473:       when Symbol
    474:         s, t, a = split_symbol(table_name)
    475:         [s||sch, t]
    476:       when SQL::QualifiedIdentifier
    477:         [table_name.table, table_name.column]
    478:       when SQL::Identifier
    479:         [sch, table_name.value]
    480:       when String
    481:         [sch, table_name]
    482:       else
    483:         raise Error, 'table_name should be a Symbol, SQL::QualifiedIdentifier, SQL::Identifier, or String'
    484:       end
    485:     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/query.rb, line 292
    292:     def select(*columns, &block)
    293:       columns += Array(Sequel.virtual_row(&block)) if block
    294:       m = []
    295:       columns.map do |i|
    296:         i.is_a?(Hash) ? m.concat(i.map{|k, v| SQL::AliasedExpression.new(k,v)}) : m << i
    297:       end
    298:       clone(:select => m)
    299:     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/query.rb, line 304
    304:     def select_all
    305:       clone(:select => nil)
    306:     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/query.rb, line 313
    313:     def select_more(*columns, &block)
    314:       columns = @opts[:select] + columns if @opts[:select]
    315:       select(*columns, &block)
    316:     end

select_sql()

Formats a SELECT statement

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

[Source]

         # File lib/sequel/dataset/sql.rb, line 490
    490:     def select_sql
    491:       return static_sql(@opts[:sql]) if @opts[:sql]
    492:       clause_sql(:select)
    493:     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 140
    140:     def server(servr)
    141:       clone(:server=>servr)
    142:     end

set(*args)

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

[Source]

        # File lib/sequel/dataset/actions.rb, line 84
    84:     def set(*args)
    85:       update(*args)
    86:     end

set_defaults(hash)

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

[Source]

         # File lib/sequel/dataset.rb, line 146
    146:     def set_defaults(hash)
    147:       clone(:defaults=>(@opts[:defaults]||{}).merge(hash))
    148:     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 182
    182:     def set_graph_aliases(graph_aliases)
    183:       ds = select(*graph_alias_columns(graph_aliases))
    184:       ds.opts[:graph_aliases] = graph_aliases
    185:       ds
    186:     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 152
    152:     def set_overrides(hash)
    153:       clone(:overrides=>hash.merge(@opts[:overrides]||{}))
    154:     end

single_record()

Returns the first record in the dataset.

[Source]

         # File lib/sequel/dataset/convenience.rb, line 203
    203:     def single_record
    204:       clone(:limit=>1).each{|r| return r}
    205:       nil
    206:     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 210
    210:     def single_value
    211:       if r = naked.clone(:graph=>false).single_record
    212:         r.values.first
    213:       end
    214:     end

sql()

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

[Source]

         # File lib/sequel/dataset/sql.rb, line 496
    496:     def sql
    497:       select_sql
    498:     end

subscript_sql(s)

SQL fragment for specifying subscripts (SQL arrays)

[Source]

         # File lib/sequel/dataset/sql.rb, line 501
    501:     def subscript_sql(s)
    502:       "#{literal(s.f)}[#{expression_list(s.sub)}]"
    503:     end

sum(column)

Returns the sum for the given column.

[Source]

         # File lib/sequel/dataset/convenience.rb, line 217
    217:     def sum(column)
    218:       aggregate_dataset.get{sum(column)}
    219:     end

supports_cte?()

Whether the dataset supports common table expressions (the WITH clause).

[Source]

        # File lib/sequel/dataset/features.rb, line 15
    15:     def supports_cte?
    16:       select_clause_methods.include?(WITH_SUPPORTED)
    17:     end

supports_distinct_on?()

Whether the dataset supports the DISTINCT ON clause, true by default.

[Source]

        # File lib/sequel/dataset/features.rb, line 20
    20:     def supports_distinct_on?
    21:       true
    22:     end

supports_intersect_except?()

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

[Source]

        # File lib/sequel/dataset/features.rb, line 25
    25:     def supports_intersect_except?
    26:       true
    27:     end

supports_intersect_except_all?()

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

[Source]

        # File lib/sequel/dataset/features.rb, line 30
    30:     def supports_intersect_except_all?
    31:       true
    32:     end

supports_is_true?()

Whether the dataset supports the IS TRUE syntax.

[Source]

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

supports_join_using?()

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

[Source]

        # File lib/sequel/dataset/features.rb, line 40
    40:     def supports_join_using?
    41:       true
    42:     end

supports_multiple_column_in?()

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

[Source]

        # File lib/sequel/dataset/features.rb, line 46
    46:     def supports_multiple_column_in?
    47:       true
    48:     end

supports_timestamp_timezones?()

Whether the dataset supports timezones in literal timestamps

[Source]

        # File lib/sequel/dataset/features.rb, line 51
    51:     def supports_timestamp_timezones?
    52:       false
    53:     end

supports_timestamp_usecs?()

Whether the dataset supports fractional seconds in literal timestamps

[Source]

        # File lib/sequel/dataset/features.rb, line 56
    56:     def supports_timestamp_usecs?
    57:       true
    58:     end

supports_window_functions?()

Whether the dataset supports window functions.

[Source]

        # File lib/sequel/dataset/features.rb, line 61
    61:     def supports_window_functions?
    62:       false
    63:     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 229
    229:     def to_csv(include_column_titles = true)
    230:       n = naked
    231:       cols = n.columns
    232:       csv = ''
    233:       csv << "#{cols.join(COMMA_SEPARATOR)}\r\n" if include_column_titles
    234:       n.each{|r| csv << "#{cols.collect{|c| r[c]}.join(COMMA_SEPARATOR)}\r\n"}
    235:       csv
    236:     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 242
    242:     def to_hash(key_column, value_column = nil)
    243:       inject({}) do |m, r|
    244:         m[r[key_column]] = value_column ? r[value_column] : r
    245:         m
    246:       end
    247:     end

truncate()

Truncates the dataset. Returns nil.

[Source]

        # File lib/sequel/dataset/actions.rb, line 89
    89:     def truncate
    90:       execute_ddl(truncate_sql)
    91:     end

truncate_sql()

SQL query to truncate the table

[Source]

         # File lib/sequel/dataset/sql.rb, line 506
    506:     def truncate_sql
    507:       if opts[:sql]
    508:         static_sql(opts[:sql])
    509:       else
    510:         check_modification_allowed!
    511:         raise(InvalidOperation, "Can't truncate filtered datasets") if opts[:where]
    512:         _truncate_sql(source_list(opts[:from]))
    513:       end
    514:     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 GROUP BY a

[Source]

         # File lib/sequel/dataset/query.rb, line 321
    321:     def unfiltered
    322:       clone(:where => nil, :having => nil)
    323:     end

ungraphed()

Remove the splitting of results into subhashes. Also removes metadata related to graphing, so you should not call graph any tables to this dataset after calling this method.

[Source]

         # File lib/sequel/dataset/graph.rb, line 191
    191:     def ungraphed
    192:       clone(:graph=>nil)
    193:     end

ungrouped()

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

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

[Source]

         # File lib/sequel/dataset/query.rb, line 328
    328:     def ungrouped
    329:       clone(:group => nil, :having => nil)
    330:     end

union(dataset, opts={})

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

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

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

[Source]

         # File lib/sequel/dataset/query.rb, line 341
    341:     def union(dataset, opts={})
    342:       opts = {:all=>opts} unless opts.is_a?(Hash)
    343:       compound_clone(:union, dataset, opts)
    344:     end

unlimited()

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

      dataset.limit(10, 20).unlimited # SELECT * FROM items

[Source]

         # File lib/sequel/dataset/query.rb, line 349
    349:     def unlimited
    350:       clone(:limit=>nil, :offset=>nil)
    351:     end

unordered()

Returns a copy of the dataset with no order.

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

[Source]

         # File lib/sequel/dataset/query.rb, line 356
    356:     def unordered
    357:       order(nil)
    358:     end

update(values={})

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

[Source]

        # File lib/sequel/dataset/actions.rb, line 95
    95:     def update(values={})
    96:       execute_dui(update_sql(values))
    97:     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 523
    523:     def update_sql(values = {})
    524:       return static_sql(opts[:sql]) if opts[:sql]
    525:       check_modification_allowed!
    526:       clone(:values=>values)._update_sql
    527:     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 533
    533:     def where(*cond, &block)
    534:       _filter(:where, *cond, &block)
    535:     end

window_function_sql(function, window)

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

[Source]

         # File lib/sequel/dataset/sql.rb, line 557
    557:     def window_function_sql(function, window)
    558:       "#{literal(function)} OVER #{literal(window)}"
    559:     end

window_sql(opts)

The SQL fragment for the given window‘s options.

[Source]

         # File lib/sequel/dataset/sql.rb, line 538
    538:     def window_sql(opts)
    539:       raise(Error, 'This dataset does not support window functions') unless supports_window_functions?
    540:       window = literal(opts[:window]) if opts[:window]
    541:       partition = "PARTITION BY #{expression_list(Array(opts[:partition]))}" if opts[:partition]
    542:       order = "ORDER BY #{expression_list(Array(opts[:order]))}" if opts[:order]
    543:       frame = case opts[:frame]
    544:         when nil
    545:           nil
    546:         when :all
    547:           "ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING"
    548:         when :rows
    549:           "ROWS UNBOUNDED PRECEDING"
    550:         else
    551:           raise Error, "invalid window frame clause, should be :all, :rows, or nil"
    552:       end
    553:       "(#{[window, partition, order, frame].compact.join(' ')})"
    554:     end

with(name, dataset, opts={})

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

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

[Source]

         # File lib/sequel/dataset/sql.rb, line 566
    566:     def with(name, dataset, opts={})
    567:       raise(Error, 'This datatset does not support common table expressions') unless supports_cte?
    568:       clone(:with=>(@opts[:with]||[]) + [opts.merge(:name=>name, :dataset=>dataset)])
    569:     end

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

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

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

[Source]

         # File lib/sequel/dataset/sql.rb, line 576
    576:     def with_recursive(name, nonrecursive, recursive, opts={})
    577:       raise(Error, 'This datatset does not support common table expressions') unless supports_cte?
    578:       clone(:with=>(@opts[:with]||[]) + [opts.merge(:recursive=>true, :name=>name, :dataset=>nonrecursive.union(recursive, {:all=>opts[:union_all] != false, :from_self=>false}))])
    579:     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 585
    585:     def with_sql(sql, *args)
    586:       sql = SQL::PlaceholderLiteralString.new(sql, args) unless args.empty?
    587:       clone(:sql=>sql)
    588:     end

### Protected Instance methods

_insert_sql()

Formats in INSERT statement using the stored columns and values.

[Source]

         # File lib/sequel/dataset/sql.rb, line 601
    601:     def _insert_sql
    602:       clause_sql(:insert)
    603:     end

_update_sql()

Formats an UPDATE statement using the stored values.

[Source]

         # File lib/sequel/dataset/sql.rb, line 606
    606:     def _update_sql
    607:       clause_sql(:update)
    608:     end

compound_from_self()

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

[Source]

         # File lib/sequel/dataset/sql.rb, line 612
    612:     def compound_from_self
    613:       (@opts[:limit] || @opts[:order]) ? from_self : self
    614:     end

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 162
    162:     def options_overlap(opts)
    163:       !(@opts.collect{|k,v| k unless v.nil?}.compact & opts).empty?
    164:     end

simple_select_all?()

Whether this dataset is a simple SELECT * FROM table.

[Source]

         # File lib/sequel/dataset.rb, line 167
    167:     def simple_select_all?
    168:       o = @opts.reject{|k,v| v.nil? || NON_SQL_OPTIONS.include?(k)}
    169:       o.length == 1 && (f = o[:from]) && f.length == 1 && f.first.is_a?(Symbol)
    170:     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 205
    205:     def to_prepared_statement(type, values=nil)
    206:       ps = bind
    207:       ps.extend(PreparedStatementMethods)
    208:       ps.prepared_type = type
    209:       ps.prepared_modify_values = values
    210:       ps
    211:     end

[Validate]