select e.emp_no, (a.salary-b.salary)as growth
from employees e 
join salaries a on e.emp_no=a.emp_no 
join salaries b on e.emp_no=b.emp_no 
where a.to_date='9999-01-01' and b.from_date = e.hire_date
order by growth

这题没啥思路，本来想用row_number做，但是没做出来，参考别人的答案写出来