Zkuste to prosím, doufám, že to pomůže.
DELETE FROM departure, departure_time
USING departure
INNER JOIN departure_time
WHERE departure_date = '2016-09-30'
AND departure_time.id = departure.id
Nebo
DELETE FROM departure, departure_time
USING departure
INNER JOIN departure_time
WHERE departure_date = '2016-09-30'
AND departure_time.departure_id = departure.id
Nebo můžete použít ON DELETE CASCADE
to bude fungovat automaticky za vás.