Trigger with Ids other than OLD.id - mysql

Question

I have a table like this:
user_oauth:
+----------------+-----------------+------+-----+---------+----------------+
| Field | Type | Null | Key | Default | Extra |
+----------------+-----------------+------+-----+---------+----------------+
| id | int(8) unsigned | NO | PRI | NULL | auto_increment |
| user_id | int(8) unsigned | NO | MUL | NULL | |
| google_id | varchar(30) | YES | UNI | NULL | |
| facebook_id | varchar(30) | YES | UNI | NULL | |
| windowslive_id | varchar(30) | YES | UNI | NULL | |
+----------------+-----------------+------+-----+---------+----------------+
which contains id of 3 the tables user_facebook, user_google, user_windowslive,
Example for user_facebook:
+-----------+-----------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+-----------+-----------------+------+-----+---------+-------+
| id | varchar(30) | NO | PRI | NULL | |
| email | varchar(60) | NO | UNI | NULL | |
| firstname | varchar(30) | YES | | NULL | |
| lastname | varchar(30) | YES | | NULL | |
| link | varchar(100) | YES | | NULL | |
| locale | varchar(5) | YES | | NULL | |
| picture | varchar(200) | YES | | NULL | |
| verified | int(1) unsigned | NO | | NULL | |
+-----------+-----------------+------+-----+---------+-------+
I would like to make a TRIGGER ON DELETE on user_oauth, which will delete user_facebook row if facebook_id of user_oauth is filled.
So I tried:
DELIMITER $$
CREATE TRIGGER `user_oauth_delete` BEFORE DELETE ON `user_oauth`
FOR EACH ROW BEGIN
DELETE FROM user_facebook
WHERE user_facebook.id = user_oauth.facebook_id;
END
$$
DELIMITER ;
But I have the error message:
Unknown column 'user_oauth.facebook_id' in 'where clause'
How to do it?
Thanks.
Solution
I had misunderstanding the OLD statement, so I had to:
DELIMITER $$
CREATE TRIGGER `user_oauth_delete` BEFORE DELETE ON `user_oauth`
FOR EACH ROW BEGIN
DELETE FROM user_facebook
WHERE user_facebook.id = OLD.facebook_id;
END
$$
DELIMITER ;

Answer 1

Don't do this with triggers. Do this with cascading delete constraints.
alter table oath
add constraint fk_oath_facebook
foreign key (facebookid) references user_facebook(id)
on delete cascade;
The documentation does a pretty good job of explaining constraints and the cascading capabilities.

Answer 2

Other than what have been suggested, you can as well consider wrapping both the DML statement inside a transaction block in a stored procedure and pass the facebook_id as parameter to the procedure. Such that both operation will happen in same order. Something like
DELIMITER $$
CREATE PROCEDURE `transaction_sp` (#facebook_id varchar(50))
LANGUAGE SQL
DETERMINISTIC
SQL SECURITY DEFINER
BEGIN
DECLARE exit handler for sqlexception
BEGIN
-- ERROR
ROLLBACK;
END;
DECLARE exit handler for sqlwarning
BEGIN
-- WARNING
ROLLBACK;
END;
START TRANSACTION;
DELETE FROM user_facebook WHERE id = #facebook_id;
DELETE FROM `user_oauth` WHERE facebook_id = #facebook_id;
COMMIT;
END
$$