CREATE TRIGGER 取消定票 ON  訂票
AFTER DELETE 
AS BEGIN
 
IF((SELECT 艙位類型 FROM deleted )='A')   
UPDATE 航班
SET   經濟艙剩余票數=經濟艙剩余票數+(SELECT 張數 FROM deleted )
WHERE 航班編號=(select 航班編號 from deleted )AND 登機日期=(select 登機日期 from deleted )

ELSE IF((SELECT 艙位類型 FROM deleted  )='B')
UPDATE 航班
SET   頭等艙剩余票數=頭等艙剩余票數+(SELECT 張數 FROM deleted )
WHERE 航班編號=(select 航班編號 from deleted )AND 登機日期=(select 登機日期 from deleted )


END;