本题中涉及同表相加减。 思路：首先要找出在职员工，然后根据同一员工不同时期的薪资情况进行相加减； 代码： select now1.emp_no, sum(now2.salary-now1.salary) as growth from salaries now1 join salaries now2 on now1.to_date=now2.from_date and now1.emp_no =now2.emp_no where now1.emp_no in (select emp_no from salaries where to_date='9999-01-01') group by now1.emp_no order by growth asc