select 
  DISTINCT e.emp_no,(s2.salary-s1.salary) as growth
from 
  employees as e
-- 找到入职的薪资表
join 
  salaries as s1
on 
  e.emp_no=s1.emp_no and s1.from_date=e.hire_date
-- 找到当前的薪资表
join 
  salaries as s2
on 
  e.emp_no=s2.emp_no and s2.to_date='9999-01-01'
order by 
  growth asc