Question

In Ruby on Rails, how to add foreign key constraint in migration?

Answer 1

AFAIK, there isn’t any built-in support for that, but there are several plugins that help you with that. You can also add them manually to your migration files, just use the execute method for that, e.g. (sample from Rails API):

  class MakeJoinUnique < ActiveRecord::Migration     def self.up       execute 'ALTER TABLE `pages_linked_pages` ADD UNIQUE `page_id_linked_page_id` (`page_id`,`linked_page_id`)'     end      def self.down       execute 'ALTER TABLE `pages_linked_pages` DROP INDEX `page_id_linked_page_id`'     end   end