215题解 | 利用窗口函数求各个时期的工资涨幅，再加总

# 这种做法曲解题意了，用不着employees表，并默认salaries表中from_date最小值就是入职时间
select a.emp_no 
,sum(a.growth_p) growth
--将各个小的薪资涨幅加总，即是所求
from (
    --求出每个员工，各个任职时期下的薪资涨幅
    select emp_no
    ,salary-lag(salary,1) over(partition by emp_no order by from_date) growth_p
    from salaries
    where emp_no in (
        --筛选出还在职的员工emp_no
        select emp_no
        from salaries 
        group by emp_no
        having max(to_date)="9999-01-01"
    )
) a
group by a.emp_no 
order by growth