MySQL 生成累计和

备注:测试数据库版本为MySQL 8.0

如需要scott用户下建表及录入数据语句，可参考:
scott建表及录入数据sql脚本

一.需求

计算某个列中所有值的累计和

比如，经常遇到的业务需求就是领导需要看每个月的销售额，已经累计到当月的销售额。

解决方案:
下面给出了一种解决方案，它展示了如何计算所有职员工资的累计和。

代码:

select e.ename, e.sal,
       ( select sum(d.sal)  from emp d
           where d.empno <= e.empno) as running_total
   from emp e
order by 3;

测试记录:

mysql> select e.ename, e.sal,
    ->        ( select sum(d.sal)  from emp d
    ->            where d.empno <= e.empno) as running_total
    ->    from emp e
    -> order by 3;
+--------+---------+---------------+
| ename  | sal     | running_total |
+--------+---------+---------------+
| SMITH  |  800.00 |        800.00 |
| ALLEN  | 1600.00 |       2400.00 |
| WARD   | 1250.00 |       3650.00 |
| JONES  | 2975.00 |       6625.00 |
| MARTIN | 1250.00 |       7875.00 |
| BLAKE  | 2850.00 |      10725.00 |
| CLARK  | 4000.00 |      14725.00 |
| SCOTT  | 3000.00 |      17725.00 |
| KING   | 4000.00 |      21725.00 |
| TURNER | 1500.00 |      23225.00 |
| ADAMS  | 1100.00 |      24325.00 |
| JAMES  |  950.00 |      25275.00 |
| FORD   | 3000.00 |      28275.00 |
| MILLER | 4000.00 |      32275.00 |
+--------+---------+---------------+
14 rows in set (0.00 sec)