Question

I have two tables as students and certificates, I need to delete the certificates related to a particular student from the certificates table when deleting a student from the student table. I am not much familiar with mysql triggers. please assist me.

this is what I’ve tried but I not sure it is correct

DELIMITER $$  
CREATE TRIGGER delCerts AFTER DELETE ON students
FOR EACH ROW
BEGIN
DELETE FROM certificates as certs WHERE certs.stCode = students.stCode;
END;
$$

Answer 1

In InnoDB databases you could achieve it by having foreign key in certificates table:

idStudent INT NOT NULL,
FOREIGN KEY (idStudent) REFERENCES Students (id)
  ON DELETE CASCADE
  ON UPDATE CASCADE

When you delete student from stuends table – all related certificates will be also deleted. I think it’s better than trigger, because if you or someone will disable triggers (accidentally or on purpose) your db will be inconsistent.