SELECT sum(sizeamount) as counts
,[ShopID]
,dateadd(hh, - datepart(hour,downloadtime) % 24 ,downloadtime)
FROM [abc].[dbo].[ShopDownloadAmount]
group by shopid, dateadd(hh, - datepart(hour,downloadtime) % 24 ,downloadtime)
order by dateadd(hh, - datepart(hour,downloadtime) % 24 ,downloadtime)

结果如下
36730    2    2009-12-15 00:00:00.000
72342    2    2009-12-16 00:00:00.000
76858    2    2009-12-17 00:00:00.000
34094    2    2009-12-18 00:00:00.000
58178    2    2009-12-19 00:00:00.000