如何将相同的多窗口函数组合为一个，并在查询中的任何需要的位置调用别名？

Posted 2021-04-10

如何解决在单个SQL查询中针对不同聚合多次使用相同窗口函数的问题？有没有什么方法可以对它进行别名并根据需要在查询中多次调用它。

我尝试使用'Window'子句，但SQL Server目前不支持'Window'子句。

select empid, qty, 
       sum(qty) over (partition by empid order by month rows between unbounded preceding and current row) as running_sum, 
       avg(qty) over (partition by empid order by month rows between unbounded preceding and current row) as running_avg, 
       min(qty) over (partition by empid order by month rows between unbounded preceding and current row) as running_min, 
       max(qty) over (partition by empid order by month rows between unbounded preceding and current row) as running_max
from employee

有没有办法删除代码中的冗余？

答案

不在SQL Server中，ANSI SQL支持用于定义可以重用的窗口的WINDOWS子句。但是，SQL Server不支持它。

我认为你可以略微简化你的逻辑：

select empid, qty, 
       sum(qty) over (partition by empid order by month) as running_sum, 
       avg(qty) over (partition by empid order by month) as running_avg, 
       min(qty) over (partition by empid order by month) as running_min, 
       max(qty) over (partition by empid order by month) as running_max
from employee;