select t1.emp_no,(t1.sTo-t2.sHire) as growth
from(select s.emp_no,s.salary as sTo from salaries as s inner join
employees as e on s.emp_no=e.emp_no
where s.to_date='9999-01-01') as t1,
(select s.emp_no,s.salary as sHire from salaries as s inner join
employees as e on s.emp_no=e.emp_no
where s.from_date=e.hire_date) as t2
where t1.emp_no=t2.emp_no
order by growth

表连接
首先求出当前工资金额 as 一张新的表 t1
然后求出入职时工资金额 as 一张新的表 t1
把两张表通过emp_no进行连接，order by 排序