题解 | #查找在职员工自入职以来的薪水涨幅情况#

select t2.emp_no,(t2.salary-t1.salary) as growth
from 
(select a1.emp_no emp_no,a1.salary salary
from salaries a1 join salaries a2
on a1.from_date =a2.to_date and a1.to_date="9999-01-01")t2
left join
(select a.emp_no emp_no,salary
from employees a join salaries b 
on a.hire_date =b.from_date)t1
on t2.emp_no=t1.emp_no
order by growth asc

#法2：
select a.emp_no, (b.salary - c.salary) as growth
from
	employees as a
    inner join salaries as b
    on a.emp_no = b.emp_no and b.to_date = '9999-01-01'
    inner join salaries as c
    on a.emp_no = c.emp_no and a.hire_date = c.from_date 
order by growth asc