Class: Sequel::Dataset

Inherits:
Object show all
Extended by:
Metaprogramming
Includes:
Enumerable, Metaprogramming
Defined in:
lib/sequel/dataset.rb,
lib/sequel/dataset/sql.rb,
lib/sequel/dataset/misc.rb,
lib/sequel/dataset/graph.rb,
lib/sequel/dataset/query.rb,
lib/sequel/dataset/actions.rb,
lib/sequel/dataset/features.rb,
lib/sequel/dataset/mutation.rb,
lib/sequel/extensions/query.rb,
lib/sequel/extensions/pagination.rb,
lib/sequel/extensions/pretty_table.rb,
lib/sequel/dataset/prepared_statements.rb,
lib/sequel/adapters/utils/stored_procedures.rb

Overview

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

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

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

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

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

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

For more information, see the “Dataset Basics” guide.

Defined Under Namespace

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

Constant Summary collapse

AND_SEPARATOR = 
" AND ".freeze
BOOL_FALSE = 
"'f'".freeze
BOOL_TRUE = 
"'t'".freeze
COMMA_SEPARATOR = 
', '.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]
COUNT_OF_ALL_AS_COUNT = 
SQL::Function.new(:count, LiteralString.new('*'.freeze)).as(:count)
DATASET_ALIAS_BASE_NAME = 
't'.freeze
FOR_UPDATE = 
' FOR UPDATE'.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 lock')
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 = 
LiteralString.new('*').freeze
SQL_WITH = 
"WITH ".freeze
NOTIMPL_MSG =

:section: Miscellaneous methods These methods don’t fit cleanly into another section.

"This method must be overridden in Sequel adapters".freeze
ARRAY_ACCESS_ERROR_MSG = 
'You cannot call Dataset#[] with an integer or with no arguments.'.freeze
ARG_BLOCK_ERROR_MSG = 
'Must use either an argument or a block, not both'.freeze
IMPORT_ERROR_MSG = 
'Using Sequel::Dataset#import an empty column array is not allowed'.freeze
COLUMN_CHANGE_OPTS =

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

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

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

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

These symbols have _join methods created (e.g. inner_join) that call join_table with the symbol, passing along the arguments and block from the method call.

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

These symbols have _join methods created (e.g. natural_join) that call join_table with the symbol. They only accept a single table argument which is passed to join_table, and they raise an error if called with a block.

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

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

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

Methods that return modified datasets

%w'add_graph_aliases and distinct except exclude
filter for_update from from_self graph grep group group_and_count group_by having intersect invert
limit lock_style naked or order order_append order_by order_more order_prepend paginate qualify query
reverse reverse_order select select_all select_append select_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} + JOIN_METHODS
ACTION_METHODS =

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

%w'<< [] []= all avg count columns columns! delete each
empty? fetch_rows first get import insert insert_multiple interval last
map max min multi_insert range select_hash select_map select_order_map
set single_record single_value sum to_csv to_hash truncate update'.map{|x| x.to_sym}
WITH_SUPPORTED =

Method used to check if WITH is supported

:select_with_sql
MUTATION_METHODS =

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

QUERY_METHODS
PREPARED_ARG_PLACEHOLDER =

:section: Methods related to prepared statements or bound variables On some adapters, these use native prepared statements and bound variables, on others support is emulated. For details, see the “Prepared Statements/Bound Variables” guide.

LiteralString.new('?').freeze

Instance Attribute Summary collapse

Class Method Summary collapse

Instance Method Summary collapse

Methods included from Metaprogramming

meta_def

Constructor Details

#initialize(db, opts = nil) ⇒ Dataset

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

DB[:posts]

Sequel::Dataset is an abstract class that is not useful by itself. Each database adaptor should provide a subclass of Sequel::Dataset, and have the Database#dataset method return an instance of that class.



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

def initialize(db, opts = nil)
  @db = db
  @quote_identifiers = db.quote_identifiers? if db.respond_to?(:quote_identifiers?)
  @identifier_input_method = db.identifier_input_method if db.respond_to?(:identifier_input_method)
  @identifier_output_method = db.identifier_output_method if db.respond_to?(:identifier_output_method)
  @opts = opts || {}
  @row_proc = nil
end

Instance Attribute Details

#db ⇒ Object

The database that corresponds to this dataset



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# File 'lib/sequel/dataset/misc.rb', line 14

def db
  @db
end

#identifier_input_method ⇒ Object

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



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# File 'lib/sequel/dataset/mutation.rb', line 25

def identifier_input_method
  @identifier_input_method
end

#identifier_output_method ⇒ Object

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



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

def identifier_output_method
  @identifier_output_method
end

#opts ⇒ Object

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



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

def opts
  @opts
end

#quote_identifiers=(value) ⇒ Object (writeonly)

Whether to quote identifiers for this dataset



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

def quote_identifiers=(value)
  @quote_identifiers = value
end

#row_proc ⇒ Object

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.



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

def row_proc
  @row_proc
end

Class Method Details

.clause_methods(type, clauses) ⇒ Object

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



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

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

.def_mutation_method(*meths) ⇒ Object

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



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# File 'lib/sequel/dataset/mutation.rb', line 14

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

Instance Method Details

#<<(*args) ⇒ Object

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



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

def <<(*args)
  insert(*args)
end

#[](*conditions) ⇒ Object

Returns the first record matching the conditions. Examples:

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

Raises:



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

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

#[]=(conditions, values) ⇒ Object

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

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



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# File 'lib/sequel/dataset/actions.rb', line 34

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

#add_graph_aliases(graph_aliases) ⇒ Object

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



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# File 'lib/sequel/dataset/graph.rb', line 13

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

#aliased_expression_sql(ae) ⇒ Object

SQL fragment for the aliased expression



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# File 'lib/sequel/dataset/sql.rb', line 214

def aliased_expression_sql(ae)
  as_sql(literal(ae.expression), ae.aliaz)
end

#all(&block) ⇒ Object

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



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

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

#and(*cond, &block) ⇒ Object

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

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

Raises:



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# File 'lib/sequel/dataset/query.rb', line 43

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

#array_sql(a) ⇒ Object

SQL fragment for the SQL array.



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# File 'lib/sequel/dataset/sql.rb', line 219

def array_sql(a)
  a.empty? ? '(NULL)' : "(#{expression_list(a)})"     
end

#as(aliaz) ⇒ Object

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.



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

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

#avg(column) ⇒ Object

Returns the average value for the given column.



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

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

#bind(bind_vars = {}) ⇒ Object

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



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# File 'lib/sequel/dataset/prepared_statements.rb', line 179

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

#boolean_constant_sql(constant) ⇒ Object

SQL fragment for BooleanConstants



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# File 'lib/sequel/dataset/sql.rb', line 224

def boolean_constant_sql(constant)
  literal(constant)
end

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

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.



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# File 'lib/sequel/dataset/prepared_statements.rb', line 188

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

#case_expression_sql(ce) ⇒ Object

SQL fragment for specifying given CaseExpression.



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# File 'lib/sequel/dataset/sql.rb', line 229

def case_expression_sql(ce)
  sql = '(CASE '
  sql << "#{literal(ce.expression)} " if ce.expression
  ce.conditions.collect{ |c,r|
    sql << "WHEN #{literal(c)} THEN #{literal(r)} "
  }
  sql << "ELSE #{literal(ce.default)} END)"
end

#cast_sql(expr, type) ⇒ Object

SQL fragment for the SQL CAST expression.



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# File 'lib/sequel/dataset/sql.rb', line 239

def cast_sql(expr, type)
  "CAST(#{literal(expr)} AS #{db.cast_type_literal(type)})"
end

#clone(opts = {}) ⇒ Object

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



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# File 'lib/sequel/dataset/query.rb', line 51

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

#column_all_sql(ca) ⇒ Object

SQL fragment for specifying all columns in a given table.



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# File 'lib/sequel/dataset/sql.rb', line 244

def column_all_sql(ca)
  "#{quote_schema_table(ca.table)}.*"
end

#columns ⇒ Object

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.



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# File 'lib/sequel/dataset/actions.rb', line 62

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

#columns! ⇒ Object

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



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

def columns!
  @columns = nil
  columns
end

#complex_expression_sql(op, args) ⇒ Object

SQL fragment for complex expressions



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# File 'lib/sequel/dataset/sql.rb', line 249

def complex_expression_sql(op, args)
  case op
  when *IS_OPERATORS
    r = args.at(1)
    if r.nil? || supports_is_true?
      raise(InvalidOperation, 'Invalid argument used for IS operator') unless v = IS_LITERALS[r]
      "(#{literal(args.at(0))} #{op} #{v})"
    elsif op == :IS
      complex_expression_sql(:"=", args)
    else
      complex_expression_sql(:OR, [SQL::BooleanExpression.new(:"!=", *args), SQL::BooleanExpression.new(:IS, args.at(0), nil)])
    end
  when :IN, :"NOT IN"
    cols = args.at(0)
    vals = args.at(1)
    col_array = true if cols.is_a?(Array) || cols.is_a?(SQL::SQLArray)
    if vals.is_a?(Array) || vals.is_a?(SQL::SQLArray)
      val_array = true
      empty_val_array = vals.to_a == []
    end
    if col_array
      if empty_val_array
        if op == :IN
          literal(SQL::BooleanExpression.from_value_pairs(cols.to_a.map{|x| [x, x]}, :AND, true))
        else
          literal(1=>1)
        end
      elsif !supports_multiple_column_in?
        if val_array
          expr = SQL::BooleanExpression.new(:OR, *vals.to_a.map{|vs| SQL::BooleanExpression.from_value_pairs(cols.to_a.zip(vs).map{|c, v| [c, v]})})
          literal(op == :IN ? expr : ~expr)
        else
          old_vals = vals
          vals = vals.to_a
          val_cols = old_vals.columns
          complex_expression_sql(op, [cols, vals.map!{|x| x.values_at(*val_cols)}])
        end
      else
        "(#{literal(cols)} #{op} #{literal(vals)})"
      end
    else
      if empty_val_array
        if op == :IN
          literal(SQL::BooleanExpression.from_value_pairs([[cols, cols]], :AND, true))
        else
          literal(1=>1)
        end
      else
        "(#{literal(cols)} #{op} #{literal(vals)})"
      end
    end
  when *TWO_ARITY_OPERATORS
    "(#{literal(args.at(0))} #{op} #{literal(args.at(1))})"
  when *N_ARITY_OPERATORS
    "(#{args.collect{|a| literal(a)}.join(" #{op} ")})"
  when :NOT
    "NOT #{literal(args.at(0))}"
  when :NOOP
    literal(args.at(0))
  when :'B~'
    "~#{literal(args.at(0))}"
  else
    raise(InvalidOperation, "invalid operator #{op}")
  end
end

#constant_sql(constant) ⇒ Object

SQL fragment for constants



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

def constant_sql(constant)
  constant.to_s
end

#count ⇒ Object

Returns the number of records in the dataset.



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

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

#def_mutation_method(*meths) ⇒ Object

Add a mutation method to this dataset instance.



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

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

#delete ⇒ Object

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



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

def delete
  execute_dui(delete_sql)
end

#delete_sql ⇒ Object

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)"



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

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

#distinct(*args) ⇒ Object

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

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

Raises:



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

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

#each(&block) ⇒ Object

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.



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

def each(&block)
  if @opts[:graph]
    graph_each(&block)
  elsif row_proc = @row_proc
    fetch_rows(select_sql){|r| yield row_proc.call(r)}
  else
    fetch_rows(select_sql, &block)
  end
  self
end

#each_page(page_size, &block) ⇒ Object

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

Raises:



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# File 'lib/sequel/extensions/pagination.rb', line 20

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

#each_server ⇒ Object

Yield a dataset for each server in the connection pool that is tied to that server. Intended for use in sharded environments where all servers need to be modified with the same data:

DB[:configs].where(:key=>'setting').each_server{|ds| ds.update(:value=>'new_value')}



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# File 'lib/sequel/dataset/misc.rb', line 48

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

#empty? ⇒ Boolean

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

Returns:

  • (Boolean) 


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# File 'lib/sequel/dataset/actions.rb', line 106

def empty?
  get(1).nil?
end

#except(dataset, opts = {}) ⇒ Object

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

  • :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.except(DB).sql #=> “SELECT * FROM items EXCEPT SELECT * FROM other_items”

Raises:



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# File 'lib/sequel/dataset/query.rb', line 82

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

#exclude(*cond, &block) ⇒ Object

Performs the inverse of Dataset#filter.

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



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

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

#exists ⇒ Object

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))"



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

def exists
  LiteralString.new("EXISTS (#{select_sql})")
end

#fetch_rows(sql, &block) ⇒ Object

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

Raises:



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# File 'lib/sequel/dataset/actions.rb', line 112

def fetch_rows(sql, &block)
  raise NotImplemented, NOTIMPL_MSG
end

#filter(*cond, &block) ⇒ Object

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

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

filter accepts the following argument types:

  • Hash - list of equality/inclusion expressions

  • Array - depends:

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

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

  • String - taken literally

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

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

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

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

Examples:

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



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# File 'lib/sequel/dataset/query.rb', line 150

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

#first(*args, &block) ⇒ Object

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

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}]



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# File 'lib/sequel/dataset/actions.rb', line 135

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

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

#first_source ⇒ Object

Alias of first_source_alias



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

def first_source
  first_source_alias
end

#first_source_alias ⇒ Object

The first source (primary table) for this dataset. If the dataset doesn’t have a table, raises an error. If the table is aliased, returns the aliased name.



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

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

#first_source_table ⇒ Object

The first source (primary table) for this dataset. If the dataset doesn’t have a table, raises an error. If the table is aliased, returns the original table, not the alias



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

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

#for_update ⇒ Object

Returns a cloned dataset with a :update lock style.



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# File 'lib/sequel/dataset/query.rb', line 155

def for_update
  lock_style(:update)
end

#from(*source) ⇒ Object

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



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

def from(*source)
  table_alias_num = 0
  sources = []
  source.each do |s|
    case s
    when Hash
      s.each{|k,v| sources << SQL::AliasedExpression.new(k,v)}
    when Dataset
      sources << SQL::AliasedExpression.new(s, dataset_alias(table_alias_num+=1))
    when Symbol
      sch, table, aliaz = split_symbol(s)
      if aliaz
        s = sch ? SQL::QualifiedIdentifier.new(sch.to_sym, table.to_sym) : SQL::Identifier.new(table.to_sym)
        sources << SQL::AliasedExpression.new(s, aliaz.to_sym)
      else
        sources << s
      end
    else
      sources << s
    end
  end
  o = {:from=>sources.empty? ? nil : sources}
  o[:num_dataset_sources] = table_alias_num if table_alias_num > 0
  clone(o)
end

#from_self(opts = {}) ⇒ Object

Returns a dataset selecting from the current dataset. Supplying the :alias option controls the 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"



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# File 'lib/sequel/dataset/query.rb', line 197

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

#function_sql(f) ⇒ Object

SQL fragment specifying an SQL function call



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# File 'lib/sequel/dataset/sql.rb', line 321

def function_sql(f)
  args = f.args
  "#{f.f}#{args.empty? ? '()' : literal(args)}"
end

#get(column = nil, &block) ⇒ Object

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

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



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# File 'lib/sequel/dataset/actions.rb', line 155

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

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

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

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

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

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

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

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

Arguments:

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



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

def graph(dataset, join_conditions = nil, options = {}, &block)
  # Allow the use of a model, dataset, or symbol as the first argument
  # Find the table name/dataset based on the argument
  dataset = dataset.dataset if dataset.respond_to?(:dataset)
  table_alias = options[:table_alias]
  case dataset
  when Symbol
    table = dataset
    dataset = @db[dataset]
    table_alias ||= table
  when ::Sequel::Dataset
    if dataset.simple_select_all?
      table = dataset.opts[:from].first
      table_alias ||= table
    else
      table = dataset
      table_alias ||= dataset_alias((@opts[:num_dataset_sources] || 0)+1)
    end
  else
    raise Error, "The dataset argument should be a symbol, dataset, or model"
  end

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

  # Only allow table aliases that haven't been used
  raise_alias_error.call if @opts[:graph] && @opts[:graph][:table_aliases] && @opts[:graph][:table_aliases].include?(table_alias)
  
  # Use a from_self if this is already a joined table
  ds = (!@opts[:graph] && (@opts[:from].length > 1 || @opts[:join])) ? from_self(:alias=>options[:from_self_alias] || first_source) : self
  
  # Join the table early in order to avoid cloning the dataset twice
  ds = ds.join_table(options[:join_type] || :left_outer, table, join_conditions, :table_alias=>table_alias, :implicit_qualifier=>options[:implicit_qualifier], &block)
  opts = ds.opts

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

  # Setup the initial graph data structure if it doesn't exist
  unless graph = opts[:graph]
    master = alias_symbol(ds.first_source_alias)
    raise_alias_error.call if master == table_alias
    # Master hash storing all .graph related information
    graph = opts[:graph] = {}
    # Associates column aliases back to tables and columns
    column_aliases = graph[:column_aliases] = {}
    # Associates table alias (the master is never aliased)
    table_aliases = graph[:table_aliases] = {master=>self}
    # Keep track of the alias numbers used
    ca_num = graph[:column_alias_num] = Hash.new(0)
    # All columns in the master table are never
    # aliased, but are not included if set_graph_aliases
    # has been used.
    if add_columns
      select = opts[:select] = []
      columns.each do |column|
        column_aliases[column] = [master, column]
        select.push(SQL::QualifiedIdentifier.new(master, column))
      end
    end
  end

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

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

#grep(cols, terms) ⇒ Object

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'



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

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

#group(*columns) ⇒ Object

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



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# File 'lib/sequel/dataset/query.rb', line 220

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

#group_and_count(*columns) ⇒ Object

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



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# File 'lib/sequel/dataset/query.rb', line 238

def group_and_count(*columns)
  group(*columns.map{|c| unaliased_identifier(c)}).select(*(columns + [COUNT_OF_ALL_AS_COUNT]))
end

#group_by(*columns) ⇒ Object

Alias of group



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

def group_by(*columns)
  group(*columns)
end

#having(*cond, &block) ⇒ Object

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



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# File 'lib/sequel/dataset/query.rb', line 245

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

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

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

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

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)

Raises:



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# File 'lib/sequel/dataset/actions.rb', line 183

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

  return if values.empty?
  raise(Error, IMPORT_ERROR_MSG) if columns.empty?
  
  if slice_size = opts[:commit_every] || opts[:slice]
    offset = 0
    loop do
      @db.transaction(opts){multi_insert_sql(columns, values[offset, slice_size]).each{|st| execute_dui(st)}}
      offset += slice_size
      break if offset >= values.length
    end
  else
    statements = multi_insert_sql(columns, values)
    @db.transaction{statements.each{|st| execute_dui(st)}}
  end
end

#insert(*values) ⇒ Object

Inserts values into the associated table. The returned value is generally the value of the primary key for the inserted row, but that is adapter dependent. See insert_sql.



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# File 'lib/sequel/dataset/actions.rb', line 205

def insert(*values)
  execute_insert(insert_sql(*values))
end

#insert_multiple(array, &block) ⇒ Object

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



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# File 'lib/sequel/dataset/actions.rb', line 213

def insert_multiple(array, &block)
  if block
    array.each {|i| insert(block[i])}
  else
    array.each {|i| insert(i)}
  end
end

#insert_sql(*values) ⇒ Object

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



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# File 'lib/sequel/dataset/sql.rb', line 42

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

  check_modification_allowed!

  columns = []

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

  columns = columns.map{|k| literal(String === k ? k.to_sym : k)}
  clone(:columns=>columns, :values=>values)._insert_sql
end

#inspect ⇒ Object

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



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# File 'lib/sequel/dataset/misc.rb', line 96

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

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

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

  • :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.intersect(DB).sql #=> “SELECT * FROM items INTERSECT SELECT * FROM other_items”

Raises:



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# File 'lib/sequel/dataset/query.rb', line 259

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

#interval(column) ⇒ Object

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



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# File 'lib/sequel/dataset/actions.rb', line 223

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

#invert ⇒ Object

Inverts the current filter

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

Raises:



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# File 'lib/sequel/dataset/query.rb', line 270

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

#join(*args, &block) ⇒ Object

Alias of inner_join



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

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

#join_clause_sql(jc) ⇒ Object

SQL fragment specifying a JOIN clause without ON or USING.



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# File 'lib/sequel/dataset/sql.rb', line 327

def join_clause_sql(jc)
  table = jc.table
  table_alias = jc.table_alias
  table_alias = nil if table == table_alias
  tref = table_ref(table)
  " #{join_type_sql(jc.join_type)} #{table_alias ? as_sql(tref, table_alias) : tref}"
end

#join_on_clause_sql(jc) ⇒ Object

SQL fragment specifying a JOIN clause with ON.



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# File 'lib/sequel/dataset/sql.rb', line 336

def join_on_clause_sql(jc)
  "#{join_clause_sql(jc)} ON #{literal(filter_expr(jc.on))}"
end

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

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.



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# File 'lib/sequel/dataset/query.rb', line 314

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

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

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

  join = if expr.nil? and !block_given?
    SQL::JoinClause.new(type, table, table_alias)
  elsif using_join
    raise(Sequel::Error, "can't use a block if providing an array of symbols as expr") if block_given?
    SQL::JoinUsingClause.new(expr, type, table, table_alias)
  else
    last_alias ||= @opts[:last_joined_table] || first_source_alias
    if Sequel.condition_specifier?(expr)
      expr = expr.collect do |k, v|
        k = qualified_column_name(k, table_name) if k.is_a?(Symbol)
        v = qualified_column_name(v, last_alias) if v.is_a?(Symbol)
        [k,v]
      end
    end
    if block_given?
      expr2 = yield(table_name, last_alias, @opts[:join] || [])
      expr = expr ? SQL::BooleanExpression.new(:AND, expr, expr2) : expr2
    end
    SQL::JoinOnClause.new(expr, type, table, table_alias)
  end

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

#join_using_clause_sql(jc) ⇒ Object

SQL fragment specifying a JOIN clause with USING.



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

def join_using_clause_sql(jc)
  "#{join_clause_sql(jc)} USING (#{column_list(jc.using)})"
end

#last(*args, &block) ⇒ Object

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.

Raises:



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# File 'lib/sequel/dataset/actions.rb', line 231

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

#limit(l, o = nil) ⇒ Object

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

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



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

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

  if Range === l
    o = l.first
    l = l.last - l.first + (l.exclude_end? ? 0 : 1)
  end
  l = l.to_i if l.is_a?(String) && !l.is_a?(LiteralString)
  if l.is_a?(Integer)
    raise(Error, 'Limits must be greater than or equal to 1') unless l >= 1
  end
  opts = {:limit => l}
  if o
    o = o.to_i if o.is_a?(String) && !o.is_a?(LiteralString)
    if o.is_a?(Integer)
      raise(Error, 'Offsets must be greater than or equal to 0') unless o >= 0
    end
    opts[:offset] = o
  end
  clone(opts)
end

#literal(v) ⇒ Object

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.



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# File 'lib/sequel/dataset/sql.rb', line 90

def literal(v)
  case v
  when String
    return v if v.is_a?(LiteralString)
    v.is_a?(SQL::Blob) ? literal_blob(v) : literal_string(v)
  when Symbol
    literal_symbol(v)
  when Integer
    literal_integer(v)
  when Hash
    literal_hash(v)
  when SQL::Expression
    literal_expression(v)
  when Float
    literal_float(v)
  when BigDecimal
    literal_big_decimal(v)
  when NilClass
    literal_nil
  when TrueClass
    literal_true
  when FalseClass
    literal_false
  when Array
    literal_array(v)
  when Time
    literal_time(v)
  when DateTime
    literal_datetime(v)
  when Date
    literal_date(v)
  when Dataset
    literal_dataset(v)
  else
    literal_other(v)
  end
end

#lock_style(style) ⇒ Object

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



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# File 'lib/sequel/dataset/query.rb', line 409

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

#map(column = nil, &block) ⇒ Object

Maps column values for each record in the dataset (if a column name is given), or performs the stock mapping functionality of Enumerable. 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, ...]



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# File 'lib/sequel/dataset/actions.rb', line 242

def map(column=nil, &block)
  if column
    raise(Error, ARG_BLOCK_ERROR_MSG) if block
    super(){|r| r[column]}
  else
    super(&block)
  end
end

#max(column) ⇒ Object

Returns the maximum value for the given column.



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# File 'lib/sequel/dataset/actions.rb', line 252

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

#min(column) ⇒ Object

Returns the minimum value for the given column.



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# File 'lib/sequel/dataset/actions.rb', line 257

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

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

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

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.



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# File 'lib/sequel/dataset/actions.rb', line 271

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

#multi_insert_sql(columns, values) ⇒ Object

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

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



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# File 'lib/sequel/dataset/sql.rb', line 134

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

#naked ⇒ Object

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



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

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

#negative_boolean_constant_sql(constant) ⇒ Object

SQL fragment for NegativeBooleanConstants



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

def negative_boolean_constant_sql(constant)
  "NOT #{boolean_constant_sql(constant)}"
end

#or(*cond, &block) ⇒ Object

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

Raises:



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# File 'lib/sequel/dataset/query.rb', line 425

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

#order(*columns, &block) ⇒ Object

Returns a copy of the dataset with the order changed. If 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'



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# File 'lib/sequel/dataset/query.rb', line 445

def order(*columns, &block)
  columns += Array(Sequel.virtual_row(&block)) if block
  clone(:order => (columns.compact.empty?) ? nil : columns)
end

#order_append(*columns, &block) ⇒ Object

Alias of order_more, for naming consistency with order_prepend.



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# File 'lib/sequel/dataset/query.rb', line 451

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

#order_by(*columns, &block) ⇒ Object

Alias of order



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# File 'lib/sequel/dataset/query.rb', line 456

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

#order_more(*columns, &block) ⇒ Object

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

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'



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# File 'lib/sequel/dataset/query.rb', line 465

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

#order_prepend(*columns, &block) ⇒ Object

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

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



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# File 'lib/sequel/dataset/query.rb', line 475

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

#ordered_expression_sql(oe) ⇒ Object

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



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# File 'lib/sequel/dataset/sql.rb', line 352

def ordered_expression_sql(oe)
  "#{literal(oe.expression)} #{oe.descending ? 'DESC' : 'ASC'}"
end

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

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

Raises:



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# File 'lib/sequel/extensions/pagination.rb', line 11

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

#placeholder_literal_string_sql(pls) ⇒ Object

SQL fragment for a literal string with placeholders



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# File 'lib/sequel/dataset/sql.rb', line 357

def placeholder_literal_string_sql(pls)
  args = pls.args
  s = if args.is_a?(Hash)
    re = /:(#{args.keys.map{|k| Regexp.escape(k.to_s)}.join('|')})\b/
    pls.str.gsub(re){literal(args[$1.to_sym])}
  else
    i = -1
    pls.str.gsub(QUESTION_MARK){literal(args.at(i+=1))}
  end
  s = "(#{s})" if pls.parens
  s
end

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

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')



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# File 'lib/sequel/dataset/prepared_statements.rb', line 201

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

#print(*cols) ⇒ Object

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



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# File 'lib/sequel/extensions/pretty_table.rb', line 8

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

#provides_accurate_rows_matched? ⇒ Boolean

Whether this dataset will provide accurate number of rows matched for delete and update statements. Accurate in this case is the number of rows matched by the dataset’s filter.

Returns:

  • (Boolean) 


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# File 'lib/sequel/dataset/features.rb', line 20

def provides_accurate_rows_matched?
  true
end

#qualified_identifier_sql(qcr) ⇒ Object

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



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# File 'lib/sequel/dataset/sql.rb', line 372

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

#qualify(table = first_source) ⇒ Object

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



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# File 'lib/sequel/dataset/query.rb', line 481

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

#qualify_to(table) ⇒ Object

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



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# File 'lib/sequel/dataset/query.rb', line 489

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

#qualify_to_first_source ⇒ Object

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



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

def qualify_to_first_source
  qualify_to(first_source)
end

#query(&block) ⇒ Object

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

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

Which is the same as:

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

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



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# File 'lib/sequel/extensions/query.rb', line 30

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

#quote_identifier(name) ⇒ Object

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



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# File 'lib/sequel/dataset/sql.rb', line 379

def quote_identifier(name)
  return name if name.is_a?(LiteralString)
  name = name.value if name.is_a?(SQL::Identifier)
  name = input_identifier(name)
  name = quoted_identifier(name) if quote_identifiers?
  name
end

#quote_identifiers? ⇒ Boolean

Whether this dataset quotes identifiers.

Returns:

  • (Boolean) 


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# File 'lib/sequel/dataset/features.rb', line 13

def quote_identifiers?
  @quote_identifiers
end

#quote_schema_table(table) ⇒ Object

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



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# File 'lib/sequel/dataset/sql.rb', line 389

def quote_schema_table(table)
  schema, table = schema_and_table(table)
  "#{"#{quote_identifier(schema)}." if schema}#{quote_identifier(table)}"
end

#quoted_identifier(name) ⇒ Object

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



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

def quoted_identifier(name)
  "\"#{name.to_s.gsub('"', '""')}\""
end

#range(column) ⇒ Object

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



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

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

#requires_sql_standard_datetimes? ⇒ Boolean

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

Returns:

  • (Boolean) 


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# File 'lib/sequel/dataset/features.rb', line 26

def requires_sql_standard_datetimes?
  false
end

#reverse(*order) ⇒ Object

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



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# File 'lib/sequel/dataset/query.rb', line 511

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

#reverse_order(*order) ⇒ Object

Alias of reverse



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# File 'lib/sequel/dataset/query.rb', line 516

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

#schema_and_table(table_name) ⇒ Object

Split the schema information from the table



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# File 'lib/sequel/dataset/sql.rb', line 402

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

#select(*columns, &block) ⇒ Object

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

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



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# File 'lib/sequel/dataset/query.rb', line 527

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

#select_all ⇒ Object

Returns a copy of the dataset selecting the wildcard.

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



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# File 'lib/sequel/dataset/query.rb', line 539

def select_all
  clone(:select => nil)
end

#select_append(*columns, &block) ⇒ Object

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

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



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

def select_append(*columns, &block)
  cur_sel = @opts[:select]
  cur_sel = [WILDCARD] if !cur_sel || cur_sel.empty?
  select(*(cur_sel + columns), &block)
end

#select_hash(key_column, value_column) ⇒ Object

Returns a hash with key_column values as keys and value_column values as values. Similar to to_hash, but only selects the two columns.



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# File 'lib/sequel/dataset/actions.rb', line 287

def select_hash(key_column, value_column)
  select(key_column, value_column).to_hash(hash_key_symbol(key_column), hash_key_symbol(value_column))
end

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

Selects the column given (either as an argument or as a block), and returns an array of all values of that column in the dataset. If you give a block argument that returns an array with multiple entries, the contents of the resulting array are undefined.



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# File 'lib/sequel/dataset/actions.rb', line 295

def select_map(column=nil, &block)
  ds = naked.ungraphed
  ds = if column
    raise(Error, ARG_BLOCK_ERROR_MSG) if block
    ds.select(column)
  else
    ds.select(&block)
  end
  ds.map{|r| r.values.first}
end

#select_more(*columns, &block) ⇒ Object

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

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



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# File 'lib/sequel/dataset/query.rb', line 563

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

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

The same as select_map, but in addition orders the array by the column.



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# File 'lib/sequel/dataset/actions.rb', line 307

def select_order_map(column=nil, &block)
  ds = naked.ungraphed
  ds = if column
    raise(Error, ARG_BLOCK_ERROR_MSG) if block
    ds.select(column).order(unaliased_identifier(column))
  else
    ds.select(&block).order(&block)
  end
  ds.map{|r| r.values.first}
end

#select_sql ⇒ Object

Formats a SELECT statement

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



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

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

#server(servr) ⇒ Object

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



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

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

#set(*args) ⇒ Object

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



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# File 'lib/sequel/dataset/actions.rb', line 320

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

#set_defaults(hash) ⇒ Object

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



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# File 'lib/sequel/dataset/query.rb', line 577

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

#set_graph_aliases(graph_aliases) ⇒ Object

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



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# File 'lib/sequel/dataset/graph.rb', line 189

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

#set_overrides(hash) ⇒ Object

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



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

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

#single_record ⇒ Object

Returns the first record in the dataset.



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

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

#single_value ⇒ Object

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



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

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

#sql ⇒ Object

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



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

def sql
  select_sql
end

#subscript_sql(s) ⇒ Object

SQL fragment for specifying subscripts (SQL arrays)



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# File 'lib/sequel/dataset/sql.rb', line 420

def subscript_sql(s)
  "#{literal(s.f)}[#{expression_list(s.sub)}]"
end

#sum(column) ⇒ Object

Returns the sum for the given column.



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# File 'lib/sequel/dataset/actions.rb', line 339

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

#supports_cte? ⇒ Boolean

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

Returns:

  • (Boolean) 


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

def supports_cte?
  select_clause_methods.include?(WITH_SUPPORTED)
end

#supports_distinct_on? ⇒ Boolean

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

Returns:

  • (Boolean) 


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

def supports_distinct_on?
  false
end

#supports_intersect_except? ⇒ Boolean

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

Returns:

  • (Boolean) 


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

def supports_intersect_except?
  true
end

#supports_intersect_except_all? ⇒ Boolean

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

Returns:

  • (Boolean) 


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

def supports_intersect_except_all?
  true
end

#supports_is_true? ⇒ Boolean

Whether the dataset supports the IS TRUE syntax.

Returns:

  • (Boolean) 


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# File 'lib/sequel/dataset/features.rb', line 51

def supports_is_true?
  true
end

#supports_join_using? ⇒ Boolean

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

Returns:

  • (Boolean) 


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

def supports_join_using?
  true
end

#supports_modifying_joins? ⇒ Boolean

Whether modifying joined datasets is supported.

Returns:

  • (Boolean) 


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

def supports_modifying_joins?
  false
end

#supports_multiple_column_in? ⇒ Boolean

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

Returns:

  • (Boolean) 


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

def supports_multiple_column_in?
  true
end

#supports_timestamp_timezones? ⇒ Boolean

Whether the dataset supports timezones in literal timestamps

Returns:

  • (Boolean) 


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

def supports_timestamp_timezones?
  false
end

#supports_timestamp_usecs? ⇒ Boolean

Whether the dataset supports fractional seconds in literal timestamps

Returns:

  • (Boolean) 


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

def supports_timestamp_usecs?
  true
end

#supports_window_functions? ⇒ Boolean

Whether the dataset supports window functions.

Returns:

  • (Boolean) 


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

def supports_window_functions?
  false
end

#to_csv(include_column_titles = true) ⇒ Object

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

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



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# File 'lib/sequel/dataset/actions.rb', line 351

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

#to_hash(key_column, value_column = nil) ⇒ Object

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



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

def to_hash(key_column, value_column = nil)
  inject({}) do |m, r|
    m[r[key_column]] = value_column ? r[value_column] : r
    m
  end
end

#truncate ⇒ Object

Truncates the dataset. Returns nil.



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# File 'lib/sequel/dataset/actions.rb', line 372

def truncate
  execute_ddl(truncate_sql)
end

#truncate_sql ⇒ Object

SQL query to truncate the table



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

def truncate_sql
  if opts[:sql]
    static_sql(opts[:sql])
  else
    check_modification_allowed!
    raise(InvalidOperation, "Can't truncate filtered datasets") if opts[:where]
    _truncate_sql(source_list(opts[:from]))
  end
end

#unfiltered ⇒ Object

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



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# File 'lib/sequel/dataset/query.rb', line 590

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

#ungraphed ⇒ Object

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.



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# File 'lib/sequel/dataset/graph.rb', line 198

def ungraphed
  clone(:graph=>nil)
end

#ungrouped ⇒ Object

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



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# File 'lib/sequel/dataset/query.rb', line 597

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

#union(dataset, opts = {}) ⇒ Object

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

  • :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.union(DB).sql #=> “SELECT * FROM items UNION SELECT * FROM other_items”



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# File 'lib/sequel/dataset/query.rb', line 610

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

#unlimited ⇒ Object

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

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



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

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

#unordered ⇒ Object

Returns a copy of the dataset with no order.

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



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# File 'lib/sequel/dataset/query.rb', line 625

def unordered
  order(nil)
end

#unused_table_alias(table_alias) ⇒ Object

Creates a unique table alias that hasn’t already been used in the dataset. table_alias can be any type of object accepted by alias_symbol. The symbol returned will be the implicit alias in the argument, possibly appended with “_N” if the implicit alias has already been used, where N is an integer starting at 0 and increasing until an unused one is found.



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# File 'lib/sequel/dataset/misc.rb', line 106

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

#update(values = {}) ⇒ Object

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



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# File 'lib/sequel/dataset/actions.rb', line 378

def update(values={})
  execute_dui(update_sql(values))
end

#update_sql(values = {}) ⇒ Object

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.



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# File 'lib/sequel/dataset/sql.rb', line 169

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

#where(*cond, &block) ⇒ Object

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

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



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# File 'lib/sequel/dataset/query.rb', line 633

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

#window_function_sql(function, window) ⇒ Object

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



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# File 'lib/sequel/dataset/sql.rb', line 444

def window_function_sql(function, window)
  "#{literal(function)} OVER #{literal(window)}"
end

#window_sql(opts) ⇒ Object

The SQL fragment for the given window’s options.

Raises:



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# File 'lib/sequel/dataset/sql.rb', line 425

def window_sql(opts)
  raise(Error, 'This dataset does not support window functions') unless supports_window_functions?
  window = literal(opts[:window]) if opts[:window]
  partition = "PARTITION BY #{expression_list(Array(opts[:partition]))}" if opts[:partition]
  order = "ORDER BY #{expression_list(Array(opts[:order]))}" if opts[:order]
  frame = case opts[:frame]
    when nil
      nil
    when :all
      "ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING"
    when :rows
      "ROWS UNBOUNDED PRECEDING"
    else
      raise Error, "invalid window frame clause, should be :all, :rows, or nil"
  end
  "(#{[window, partition, order, frame].compact.join(' ')})"
end

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

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

Raises:



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

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

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

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

  • :args - Specify the arguments/columns for the CTE, should be an array of symbols.

  • :union_all - Set to false to use UNION instead of UNION ALL combining the nonrecursive and recursive parts.

Raises:



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# File 'lib/sequel/dataset/query.rb', line 652

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

#with_sql(sql, *args) ⇒ Object

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

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



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

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