单表自连接,没啥思路,就恩做,表1也没用到.我是不是很呆

select s1.emp_no,sum(s2.salary-s1.salary) as growth
from salaries s1 join salaries s2
on s1.to_date= s2.from_date 
group by s1.emp_no
having s1.emp_no in (
    select emp_no 
    from salaries 
    where to_date='9999-01-01')
order by growth