WhereChain objects act as placeholder for queries in whichwhere does not have any parameter. In this case,where can be chained to return a new relation.
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
You can define join type in the scope andassociated will not use ‘JOIN` by default.
Post.left_joins(:author).where.associated(:author)# SELECT "posts".* FROM "posts"# LEFT OUTER JOIN "authors" "authors"."id" = "posts"."author_id"# WHERE "authors"."id" IS NOT NULLPost.left_joins(:comments).where.associated(:author)# SELECT "posts".* FROM "posts"# INNER JOIN "authors" ON "authors"."id" = "posts"."author_id"# LEFT OUTER JOIN "comments" ON "comments"."post_id" = "posts"."id"# WHERE "author"."id" IS NOT NULL
# File activerecord/lib/active_record/relation/query_methods.rb, line 88defassociated(*associations)associations.eachdo|association|reflection =scope_association_reflection(association)unless@scope.joins_values.include?(reflection.name)||@scope.left_outer_joins_values.include?(reflection.name)@scope.joins!(association)endassociation_conditions =Array(reflection.association_primary_key).index_with(nil)ifreflection.options[:class_name]self.not(association=>association_conditions)elseself.not(reflection.table_name=>association_conditions)endend@scopeend
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 124defmissing(*associations)associations.eachdo|association|reflection =scope_association_reflection(association)@scope.left_outer_joins!(association)association_conditions =Array(reflection.association_primary_key).index_with(nil)ifreflection.options[:class_name]@scope.where!(association=>association_conditions)else@scope.where!(reflection.table_name=>association_conditions)endend@scopeend
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. SeeQueryMethods#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 NULLUser.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')# => []