First, there's a problem with your code. SQL Server stores datetime values with millisecond portion and your select will miss records with time > '23:59:59.000'. I usualy do this way

SET @AddDate  = '2009-02-14 00:00:00'
SET @AddDate2 =  @AddDate + 1     -- +1 day
SELECT COUNT(*) AS CountHit FROM Hit WHERE Hit.AddDate >= @AddDate AND Hit.AddDate < @AddDate2 GROUP BY AddUser

Second, it's not clear what into you store into StatisticDaily.User table because your query returns # of hits per user not the # of unique users.

BTW, aren't you using SQL 2008?

>This is a command that I execute to update some statistics on a daily basis:
>
>

>DECLARE @AddDate DateTime
>DECLARE @AddDate2 DateTime
>
>SET @AddDate='2009-02-14 00:00:00'
>SET @AddDate2='2009-02-14 23:59:59'
>
>SELECT COUNT(*) AS CountHit FROM Hit WHERE Hit.AddDate>=@AddDate AND Hit.AddDate<=@AddDate2 GROUP BY AddUser
>

>
>So, in this example, I can gather the amount of unique users for today. Then, I save that into StatisticDaily.User. Among a set of fields already in place, that one has been added recently. So, basically, for all previous records, the values in the StatisticDaily.User is empty. I need to execute an update command that will update the StatisticDaily.User field for all previous records. So, what would be the syntax for an update command to achieve this task for all previous records?