SQL移动平均线

在sql中如何创建移动平均线？

当前表：

Date             Clicks 
2012-05-01       2,230
2012-05-02       3,150
2012-05-03       5,520
2012-05-04       1,330
2012-05-05       2,260
2012-05-06       3,540
2012-05-07       2,330

所需表或输出：

Date             Clicks    3 day Moving Average
2012-05-01       2,520          4,360
2012-05-04       1,330          3,260          3,120
2012-05-06       3,540          3,320
2012-05-07       2,010

解决方法

一种方法是在同一张表上加入几次.

select
 (Current.Clicks 
  + isnull(P1.Clicks,0)
  + isnull(P2.Clicks,0)
  + isnull(P3.Clicks,0)) / 4 as MovingAvg3
from
 MyTable as Current
 left join MyTable as P1 on P1.Date = DateAdd(day,-1,Current.Date)
 left join MyTable as P2 on P2.Date = DateAdd(day,-2,Current.Date)
 left join MyTable as P3 on P3.Date = DateAdd(day,-3,Current.Date)

调整ON-Clauses的DateAdd组件以匹配您是否希望将移动平均值严格从过去到现在或几天前到几天.

>对于只需要几个数据点的移动平均值的情况,这很适用.>这不是用多个数据点移动平均线的最佳解决方案.