SQL:工资的累计

可以先进行表连接再用group by 获取running_total 代码如下：select s.emp_no, s.salary, t.running_total from salaries as s left join (select s1.emp_no, sum(s2.salary) as running_total from (select emp_no, salary from salaries where to_date='9999-01-01' ) as s1 left join (select emp_no, salary from salaries where to_date='9999-01-01' ) as s2 on s1.emp_no >=s2.emp_no group by s1.emp_no) as t on s.emp_no = t.emp_no where to_date = '9999-01-01'

这个遍历的方法有bug，必须按照emp_no的顺序执行，不然会出错

补充第一种方法的另一种写法 select s.emp_no2 ,s.salary2 ,sum(s.salary1) from ( select s1.emp_no as emp_no1, s1.salary as salary1 , s2.emp_no as emp_no2, s2.salary as salary2 from salaries s1, salaries s2 where s1.to_date = '9999-01-01' and s2.to_date = '9999-01-01' and s1.emp_no <= s2.emp_no ) as s group by s.emp_no2,s.salary2

关联子查询计算出每一行的累加数，妙，另外跟楼上探讨下，个人认为即使主键ID不是数字，也可以根据其他排序规则判断，因为累加肯定是依据某种排序规则的。

这个只能对数值类型的主键（emp_no）有效，万一主键id是uuid类型就不适应

这方法不懂

人看晕了

这样看在select里直接选出来数据，实在看不出如何join在一起的

牛B