题解 | #统计salary的累计和running_total#
统计salary的累计和running_total
http://www.nowcoder.com/practice/58824cd644ea47d7b2b670c506a159a6
重点在累计求和,通过左连接得到该员工前N-1个的工资并以该员工的工号分组前N-1个工资和自己的工资求和
select s1.emp_no,s1.salary, sum(s2.salary) as running_total 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 group by s1.emp_no order by s1.emp_no