How to enforce referential integrity on Single Table Inheritance?

Question

I\'ve read some of Bill Karwin\'s answers about single table inheritance and think this approach would be good for the setup I am considering:

Playlist
--------
         


        

Answer 1

What you can do is implement triggers on your Users and Team tables that execute whenever rows get deleted from either:

User table:

DELIMITER $$
CREATE TRIGGER user_playlist_delete 
BEFORE DELETE ON User FOR EACH ROW
BEGIN
    DELETE a FROM Playlist a
    INNER JOIN UserPlaylist b ON a.id = b.id AND b.userId = OLD.id;
END$$
DELIMITER ;

Team table:

DELIMITER $$
CREATE TRIGGER team_playlist_delete 
BEFORE DELETE ON Team FOR EACH ROW
BEGIN
    DELETE a FROM Playlist a
    INNER JOIN TeamPlaylist b ON a.id = b.id AND b.teamId = OLD.id;
END$$
DELIMITER ;

What these triggers will do is each time a record is deleted from one of these tables, a DELETE operation will automatically execute on the Playlists table using the id that's about to be deleted (via an inner join).

I have tested this and it works great.