ASA里如何实现Oracle里面的:new. / ld.的功能
请举例

CREATE TRIGGER tr_manager
BEFORE UPDATE OF dept_head_id
ON department
REFERENCING OLD AS old_dept NEW AS new_dept
FOR EACH ROW
BEGIN
   UPDATE employee
   SET employee.manager_id=new_dept.dept_head_id
   WHERE employee.dept_id=old_dept.dept_id
END