Why does my Trigger not work for CASCADE-Actions?

[Martin Fernau]

Hello!

As an example: I have three tables (all InnoDB). Table a,b and c
table `b` has a foreign-Key referenced to table `a`. For this reference I declared the CASCADE-Action on DELETE. See here:

CREATE TABLE `a` (
`id` int(11) NOT NULL auto_increment,
`name` varchar(50) NOT NULL,
PRIMARY KEY (`id`)
) ENGINE=InnoDB;

CREATE TABLE `b` (
`id` int(11) NOT NULL auto_increment,
`id_fk` int(11) NOT NULL,
`name` varchar(50) NOT NULL,
PRIMARY KEY (`id`),
KEY `id_fk` (`id_fk`)
) ENGINE=InnoDB;

ALTER TABLE `b`
ADD CONSTRAINT `b_idfk_1` FOREIGN KEY (`id_fk`) REFERENCES `a` (`id`) ON DELETE CASCADE;

Table `c` is nothing more than a simple log-Table like:
CREATE TABLE `c` (
`id_fk` int(11) NOT NULL,
`log` varchar(255) NOT NULL
) ENGINE=InnoDB;

What I now try to have is a trigger, which logs all deleted rows of table `b` like this:

delimiter |
CREATE TRIGGER b_del BEFORE DELETE ON b
FOR EACH ROW BEGIN
insert into c (id_fk, log) VALUES (OLD.id, OLD.name);
END;
|
delimiter ;

... which works, if I manually delete a row of `b`. But if I delte a row of `a` which automaticly delete a row of `b`, the trigger won't executed. Why?

Regards,
Martin