SQL Server 按每小时日期时间计数进行分组？

    create table #Events
(
    EventID int identity primary key,
    StartDate datetime not null,
    EndDate datetime not null
)
go
insert into #Events (StartDate, EndDate)
select '2007-01-01 12:44:12 AM', '2007-01-01 12:45:34 AM' union all
select '2007-01-01 12:45:12 AM', '2007-01-01 12:46:34 AM' union all
select '2007-01-01 12:46:12 AM', '2007-01-01 12:47:34 AM' union all
select '2007-01-02 5:01:08 AM', '2007-01-02 5:05:37 AM' union all
select '2007-01-02 5:50:08 AM', '2007-01-02 5:55:59 AM' union all
select '2007-01-03 4:34:12 AM', '2007-01-03 4:55:18 AM' union all
select '2007-01-07 3:12:23 AM', '2007-01-07 3:52:25 AM'

（向http://www.sqlteam.com/article/working-with-time-spans-and-durations-in-sql-server http://www.sqlteam.com/article/working-with-time-spans-and-durations-in-sql-server用于收集他们的基本 sql）

我试图找到一小时内发生的事件的计数，因此结果集将如下所示：

2007-01-01      12:00     3
2007-01-02       5:00     2
2007-01-03       4:00     1
2007-01-07       3:00     1

我一直在玩 dateadd 和 round 和 group 但没有得到它。有人可以帮忙吗？

Thanks.

这个怎么样？假设 SQL Server 2008：

SELECT CAST(StartDate as date) AS ForDate,
       DATEPART(hour,StartDate) AS OnHour,
       COUNT(*) AS Totals
FROM #Events
GROUP BY CAST(StartDate as date),
       DATEPART(hour,StartDate)

2008 年之前：

SELECT DATEADD(day,datediff(day,0,StartDate),0)   AS ForDate,
       DATEPART(hour,StartDate) AS OnHour,
       COUNT(*) AS Totals
FROM #Events
GROUP BY CAST(StartDate as date),
       DATEPART(hour,StartDate)

这导致：

ForDate                 | OnHour | Totals
-----------------------------------------
2011-08-09 00:00:00.000     12       3