使用MySQL在每个组中合计运行

在MySQL中，最有效的方法是使用变量：

select e.*,       (@s := if(@id = e.id, @s + salary,      if(@id := e.id, salary, salary)     )       ) as running_salaryfrom (select e.*      from employee e      order by e.id, e.month     ) e cross join     (select @id := -1, @s := 0) params;

您也可以使用相关子查询来执行此操作：

select e.*,       (select sum(e2.salary)        from employee e2        where e2.id = e.id and e2.month <= e.month       ) as running_salaryfrom employee e;