mysql - 如何对mysql中已经求和的别名列进行求和

Question

我有 mysql 查询。

select d.department_id,d.department_name,sum(e.salary) AS amount
from department d inner join employee e on d.department_id=e.department_id
group by d.department_id,d.department_name

我通过使用此查询获得总计。

select d.department_id,d.department_name,sum(e.salary) AS amount
from department d inner join employee e on d.department_id=e.department_id
group by d.department_id,d.department_name WITH ROLLUP

但我想要这样的总金额列别名，如下

select d.department_id,d.department_name,sum(e.salary) AS amount, sum(SELECT(amount)) AS grand_total
from department d inner join employee e on d.department_id=e.department_id
group by d.department_id,d.department_name

我的数据库结构是。

我的 table 是

但我想要这样。

请帮助我任何人。

Answer 1

如果您想要附加列，请使用连接或子查询:

select d.department_id, d.department_name, sum(e.salary) AS amount,
       tot.salary
from department d inner join
     employee e
     on d.department_id = e.department_id inner join
     (select sum(e.salary) as salary from employee) tot
group by d.department_id, d.department_name, tot.salary;

注意:这假设员工表中的总计是您想要的总计。这似乎是一个合理的假设，但如果某些员工没有部门或某些员工在多个部门工作，则可能不准确。在这种情况下，您只需在子查询中重复 join 到 department 即可。