MySQL Trigger: Delete From Table AFTER DELETE

Question

Scope: Two tables. When a new patron is created, they have some information about them stored into a 2nd table (This was done using a trigger as well, it works as expected). Here's an example of my table structure and relationship.

Table 1-> patrons

+-----+---------+-----+ +  id +   name  + val + +=====+=========+=====+ +  37 +  george +  x  + +-----+---------+-----+ +  38 +  sally  +  y  + +-----+---------+-----+ 

Table 2 -> patron_info

+----+-----+----------+ + id + pid +   name   + +----+-----+----------+ +  1 +  37 +  george  + +----+-----+----------+ +  2 +  38 +  sally   + +----+-----+----------+ 

The administrator can manage the patrons. When they choose to remove a patron, the patron is removed from the table 1 patrons. At this point, nothing happens to table 2 patron_info.

I'm simply trying to create a trigger to delete from table 2, when table 1 has an item deleted. Here's what I've tried...

Initially, I try to drop the trigger if it exists (just to clear the air)...

DROP TRIGGER IF EXISTS log_patron_delete; 

Then I try to create the trigger afterwards...

CREATE TRIGGER log_patron_delete AFTER DELETE on patrons FOR EACH ROW BEGIN DELETE FROM patron_info     WHERE patron_info.pid = patrons.id END 

At this point, I get a syntax error 1046: Check syntax near END on line 6. I don't know what the error is at this point. I've tried several different variations. Also, am I required to use a delimiter here?

Can anyone help restore my sanity?

Answer 1

I think there is an error in the trigger code. As you want to delete all rows with the deleted patron ID, you have to use old.id (Otherwise it would delete other IDs)

Try this as the new trigger:

CREATE TRIGGER log_patron_delete AFTER DELETE on patrons FOR EACH ROW BEGIN DELETE FROM patron_info     WHERE patron_info.pid = old.id; END 

Dont forget the ";" on the delete query. Also if you are entering the TRIGGER code in the console window, make use of the delimiters also.