按从4 am到4 a.m SQL Server的值进行分组

Question

我的数据来自04/01/2012 00:00至05/01/2012 05:00

让我们说

StartDate              Value 
04/01/2012 00:00       10 
04/01/2012 05:00       10 
04/01/2012 08:00       10

05/01/2012 01:00       10
05/01/2012 04:00       10
05/01/2012 05:00       10

如果我按日期分组

SUM(Value)...
GROUP BY YEAR(StartDate), MONTH(StartDate),DAY(StartDate)

此组数据从04/01/2012 00:00到05/01/2012 00:00并且总和全天值即30

但我需要按时间分组

即04/01/2012 04:00至05/01/2012 04:00以便结果为40

如何实现这一目标。任何人之前都这样做过......

Answer 1

SUM(Value)
...
GROUP BY CAST(DATEADD(hour, -4, MyDateCol) AS Date)

Answer 2

select dateadd(hh, 4, date) as date, total from (
    select
        dateadd(dd, datediff(dd, 0, dateadd(hh, -4, startDate)), 0) as date, 
        sum(value) as total
    from yourTable 
    group by dateadd(dd, datediff(dd, 0, dateadd(hh, -4, startDate)), 0)
) t

结果：

date                    total
2012-01-03 04:00:00.000 10
2012-01-04 04:00:00.000 30
2012-01-05 04:00:00.000 20