计算每个月最近12个月的平均值？

Question

我有一个带有以下值的SQL Server表：

 CREATE TABLE [dbo].[MonthleyAvarage](
    [Boxes] [int] NULL,
    [DateMonthly] [date] NULL
) ON [PRIMARY]
GO

insert into MonthleyAvarage ([Boxes],[DateMonthly]) values (1,'01/01/2010')
insert into MonthleyAvarage ([Boxes],[DateMonthly]) values (10,'02/01/2010')
insert into MonthleyAvarage ([Boxes],[DateMonthly]) values (5,'03/01/2010')
insert into MonthleyAvarage ([Boxes],[DateMonthly]) values (9,'04/01/2010')
insert into MonthleyAvarage ([Boxes],[DateMonthly]) values (3,'05/01/2010')
insert into MonthleyAvarage ([Boxes],[DateMonthly]) values (7,'06/01/2010')
insert into MonthleyAvarage ([Boxes],[DateMonthly]) values (5,'07/01/2010')
insert into MonthleyAvarage ([Boxes],[DateMonthly]) values (4,'08/01/2010')
insert into MonthleyAvarage ([Boxes],[DateMonthly]) values (55,'09/01/2010')
insert into MonthleyAvarage ([Boxes],[DateMonthly]) values (6,'10/01/2010')
insert into MonthleyAvarage ([Boxes],[DateMonthly]) values (8,'11/01/2010')
insert into MonthleyAvarage ([Boxes],[DateMonthly]) values (0,'12/01/2010')
insert into MonthleyAvarage ([Boxes],[DateMonthly]) values (2,'01/01/2011')
insert into MonthleyAvarage ([Boxes],[DateMonthly]) values (1,'02/01/2011')

我试图计算每个月的最近12个月的平均值，但我只能得出此平均值，而不仅仅是最近12个月的累计平均值

select AVG(Boxes) over (order by DATEADD(MONTH, DATEDIFF(MONTH, 0, DateMonthly), -12)) as avarage,DateMonthly,Boxes 
from monthleyavarage

我如何才能度过最近的12个月？要这样：

我该怎么做？

Answer 1

您可以在适当的window子句中使用window函数：

select 
    boxes,
    dateMonthly,
    avg(boxes) 
        over(order by dateMonthly rows between 11 preceding and current row) avg_boxes
from monthleyavarage

这将为您提供当月和前11个月的平均值。