Wystarczy określić, w których tabelach zastosować DELETE .
Usuń tylko deadline wiersze:
DELETE `deadline` FROM `deadline` LEFT JOIN `job` ....
Usuń deadline i job wiersze:
DELETE `deadline`, `job` FROM `deadline` LEFT JOIN `job` ....
Usuń tylko job wiersze:
DELETE `job` FROM `deadline` LEFT JOIN `job` ....