DELETE FROM job_history jh
WHERE employee_id =
( SELECT employee_id
FROM employees e
WHERE jh.employee_id=e.employee_id
AND start_date =
(SELECT MIN(start_date)
FROM job_history jh
WHERE jh.emplozee_id=e.employee_id)
AND 5> (SELECT count(*)
FROM job_history jh
WHERE jh.employee_id=e.employee_id
GROUP BY employee_id
HAVING COUNT(*) >= 4));