I am not very proud of what I am about to show you but it must be done
Back on April 25, 2011 I wrote this post : http://dba.stackexchange.com/questions/2368/trigger-in-mysql/2371#2371Trigger in MySQL to prevent insertion
It explains how to interrupt a trigger midstream. You do so by deliberately launching an SQL statement that is syntactically correct but breaks on execution. This still was originally suggested on pages 254-256 of the book
because SIGNAL processing is not properly implemented (OK it wasn't implemented a lick)
With regard to your
something like code, it should look something like this:
CREATE TRIGGER chk_dates BEFORE INSERT ON `job_history` FOR EACH ROW BEGIN DECLARE x INT; IF( NEW.end_date < OLD.start_date ) THEN SELECT dummy INTO x FROM mysql.user WHERE 1=1 LIMIT 1; ELSE .../// allow the data to be entered
Give it a Try !!!