How can I add ON DELETE constraint on the table?

Question

How can I add ON DELETE constraint on the table?

Answer 1

Use ALTER TABLE+ADD CONSTRAINT. E.g. if you want to link tables members and profiles by member_id and cascade delete profiles each time the member is deleted, you can write something like this:

ALTER TABLE profiles
   ADD CONSTRAINT `fk_test`
   FOREIGN KEY (`member_id` )
   REFERENCES `members` (`member_id` )
   ON DELETE CASCADE

If you will need to update that constraint - you'll have to remove it at then create again, there's no direct way to alter it.

ALTER TABLE profiles DROP FOREIGN KEY `fk_test`