sql datetime获取每天的第一个值

Question

i have a sql server table named

Datetime
=======
column UserID(int), DateTime(datetime)

it stores attendance data for users. each user have multiple datetime data for each day. i need the first DateTime data for each day for a given user between a given date range then i need them to compare with a particular time say 08:00:00 to get the late attendance. how this can be done?

Answer 1

If understood correctly here is the query for you

SELECT  UserID,
        CONVERT(VARCHAR(10),[datetime],111) as [AttendaceDate],
        MIN([datetime]) as [Date In], DATEDIFF(mi, MIN([datetime]), Convert(Datetime, CONVERT(VARCHAR(10),[datetime],111) + ' 8:00 am')) as [Minutes Late]
  FROM  TestTable
GROUP BY UserID, CONVERT(VARCHAR(10),[datetime],111)

Answer 2

SELECT  UserID,
        CONVERT(VARCHAR(10),Dateime,111),
        MIN(Datetime)
  FROM  table
GROUP BY UserID, CONVERT(VARCHAR(10),Dateime,111)
WHERE   Datetime BETWEEN '1/1/2012' AND '1/5/2012'