Question

Let’s suppose that I have a foreign key whose actions are:

on delete set default, on update cascade

If I want to change the action, how do I specify this in the alter table options?
I have tried this:

change my_table add on delete cascade my_key;

But it gives a syntax error:

ERROR 1064 (42000): You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'on delete cascade matricola' at line 1

I want to change the default action triggered when the primary key referenced is deleted.

Answer 1

ALTER TABLE my_table DROP FOREIGN KEY my_key;
ALTER TABLE my_table ADD CONSTRAINT my_key FOREIGN KEY ('some_id') 
        REFERENCES some_table ('id') ON UPDATE CASCADE ON DELETE CASCADE;

As far as i know you have to drop your key and create new one with new rules.