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WhereChain objects act as placeholder for queries in which where does not have any parameter. In this case, where must be chained with not to return a new relation.

Methods
M
N
Class Public methods
new(scope)
# File activerecord/lib/active_record/relation/query_methods.rb, line 20
def initialize(scope)
  @scope = scope
end
Instance Public methods
missing(*args)

Returns a new relation with left outer joins and where clause to idenitfy missing relations.

For example, posts that are missing a related author:

Post.where.missing(:author)
# SELECT "posts".* FROM "posts"
# LEFT OUTER JOIN "authors" ON "authors"."id" = "posts"."author_id"
# WHERE "authors"."id" IS NULL

Additionally, multiple relations can be combined. This will return posts that are missing both an author and any comments:

Post.where.missing(:author, :comments)
# SELECT "posts".* FROM "posts"
# LEFT OUTER JOIN "authors" ON "authors"."id" = "posts"."author_id"
# LEFT OUTER JOIN "comments" ON "comments"."post_id" = "posts"."id"
# WHERE "authors"."id" IS NULL AND "comments"."id" IS NULL
# File activerecord/lib/active_record/relation/query_methods.rb, line 91
def missing(*args)
  args.each do |arg|
    reflection = @scope.klass._reflect_on_association(arg)
    opts = { reflection.table_name => { reflection.association_primary_key => nil } }
    @scope.left_outer_joins!(arg)
    @scope.where!(opts)
  end

  @scope
end
not(opts, *rest)

Returns a new relation expressing WHERE + NOT condition according to the conditions in the arguments.

not accepts conditions as a string, array, or hash. See QueryMethods#where for more details on each format.

User.where.not("name = 'Jon'")
# SELECT * FROM users WHERE NOT (name = 'Jon')

User.where.not(["name = ?", "Jon"])
# SELECT * FROM users WHERE NOT (name = 'Jon')

User.where.not(name: "Jon")
# SELECT * FROM users WHERE name != 'Jon'

User.where.not(name: nil)
# SELECT * FROM users WHERE name IS NOT NULL

User.where.not(name: %w(Ko1 Nobu))
# SELECT * FROM users WHERE name NOT IN ('Ko1', 'Nobu')
# File activerecord/lib/active_record/relation/query_methods.rb, line 44
      def not(opts, *rest)
        opts = sanitize_forbidden_attributes(opts)

        where_clause = @scope.send(:where_clause_factory).build(opts, rest)

        @scope.references!(PredicateBuilder.references(opts)) if Hash === opts

        if not_behaves_as_nor?(opts)
          ActiveSupport::Deprecation.warn(<<~MSG.squish)
            NOT conditions will no longer behave as NOR in Rails 6.1.
            To continue using NOR conditions, NOT each condition individually
            (`#{
              opts.flat_map { |key, value|
                if value.is_a?(Hash) && value.size > 1
                  value.map { |k, v| ".where.not(#{key.inspect} => { #{k.inspect} => ... })" }
                else
                  ".where.not(#{key.inspect} => ...)"
                end
              }.join
            }`).
          MSG
          @scope.where_clause += where_clause.invert(:nor)
        else
          @scope.where_clause += where_clause.invert
        end

        @scope
      end