WhereChain
objects act as placeholder for queries in which where
does not have any parameter. In this case, where
can be chained to return a new relation.
- A
- M
- N
Instance Public methods
associated(*associations) Link
Returns a new relation with joins and where clause to identify associated relations.
For example, posts that are associated to a related author:
Post.where.associated(:author)
# SELECT "posts".* FROM "posts"
# INNER JOIN "authors" ON "authors"."id" = "posts"."author_id"
# WHERE "authors"."id" IS NOT NULL
Additionally, multiple relations can be combined. This will return posts associated to both an author and any comments:
Post.where.associated(:author, :comments)
# SELECT "posts".* FROM "posts"
# INNER JOIN "authors" ON "authors"."id" = "posts"."author_id"
# INNER JOIN "comments" ON "comments"."post_id" = "posts"."id"
# WHERE "authors"."id" IS NOT NULL AND "comments"."id" IS NOT NULL
# File activerecord/lib/active_record/relation/query_methods.rb, line 76 def associated(*associations) associations.each do |association| reflection = scope_association_reflection(association) @scope.joins!(association) if reflection.options[:class_name] self.not(association => { reflection.association_primary_key => nil }) else self.not(reflection.table_name => { reflection.association_primary_key => nil }) end end @scope end
missing(*associations) Link
Returns a new relation with left outer joins and where clause to identify 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 108 def missing(*associations) associations.each do |association| reflection = scope_association_reflection(association) @scope.left_outer_joins!(association) if reflection.options[:class_name] @scope.where!(association => { reflection.association_primary_key => nil }) else @scope.where!(reflection.table_name => { reflection.association_primary_key => nil }) end end @scope end
not(opts, *rest) Link
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')
User.where.not(name: "Jon", role: "admin")
# SELECT * FROM users WHERE NOT (name == 'Jon' AND role == 'admin')
If there is a non-nil condition on a nullable column in the hash condition, the records that have nil values on the nullable column won't be returned.
User.create!(nullable_country: nil)
User.where.not(nullable_country: "UK")
# SELECT * FROM users WHERE NOT (nullable_country = 'UK')
# => []