Oracle trigger to SQL trigger

Hi,Got a Oracle script with a trigger in it and I want to have it as a SQL trigger scriptCan anyone help me with thisCREATE OR REPLACE TRIGGER MESSAGES_INS BEFORE INSERT ON MESSAGESFOR EACH ROW BEGIN IF :NEW.id IS NULL THEN SELECT SEQ_MESSAGE_ID.nextval INTO :NEW.id FROM DUAL; END IF;END;/ALTER TRIGGER MESSAGES_INS ENABLE;Thanks