Example
joins() allows you to join tables to your current model. For ex.
User.joins(:posts)
will produce the following SQL query:
"SELECT "users".* FROM "users" INNER JOIN "posts" ON "posts"."user_id" = "users"."id""
Having table joined, you will have access to it:
User.joins(:posts).where(posts: { title: "Hello world" })
Pay attention on plural form. If your relation is :has_many, then the joins() argument should be pluralized. Otherwise, use singular.
Nested joins:
User.joins(posts: :images).where(images: { caption: 'First post' })
which will produce:
"SELECT "users".* FROM "users" INNER JOIN "posts" ON "posts"."user_id" = "users"."id" INNER JOIN "images" ON "images"."post_id" = "images"."id""
