leetcode 579查询员工的累积薪水_leetcode 查找员工的累计薪水

Employee表中有一年的员工薪资信息，写一个sql来获得3个月内员工工资的累计总和，但不包括最近一个月

方法一，待验证

select a.Id,a.Month, sum(Salary) as cu_salary
from Employee as a
join Employee as b on a.Id=b.Id and a.Month<=b.Month
join(
	select Id, max(month) as max_mon
	from Employee
	) as c on a.Id=c.Id and a.month between (c.max_mon-3) and (c.max_mon-1)
group by a.Id, a.Month
order by id, Month desc
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方法二

select a.Id, max(B.Month) as Month, sum(B.Salary) as Salary
from Employee as a
join Employee as b
on a.Id=b.id and B.Month between (c.max_mon-3) and (c.max_mon-1)
group by a.Id, a.Month
order by id, Month desc
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