SQL 服务器滚动平均值

Question

select
    Date, [Close],
    avg([close]) over (order by date asc rows 4 preceding) as MA10
from 
    dbo.APPL

此查询returns 股票价格的 4 天滚动平均值。但是，如果前几天少于 4，我想将值显示为 NULL。

如何在 SQL 服务器中调整它？

Answer 1

我认为 JeffUK 的意思是做这样的事情：

select
    Date, [Close],
    case when days >= 4 then MA10 end as MA10
from
(
    select
        Date, [Close],
        avg([close]) over (order by date asc rows 4 preceding) as MA10,
        count([close]) over (order by date asc rows 4 preceding) as days
    from 
        dbo.APPL

) X

SQL 服务器滚动平均值

SQL Server rolling average

sql-server

sql-server-2014

rolling-average