>>try
>>

>>UPDATE StatisticDaily
>>		SET UserCount = uc.CountHit
>>	FROM StatisticDaily 
>>		JOIN (
>>				SELECT DATEADD(day, DATEDIFF(day, 0, AddDate), 0) AS HitDate, 
>>						COUNT(DISTINCT AddUser) AS CountHit 
>>					FROM Hit 
>>					GROUP BY DATEADD(day, DATEDIFF(day, 0, AddDate),0)
>>				) uc ON uc.HitDate = StatisticDaily.date
>>

>
>This is one of the greatest SQL command I have ever seen. I really do not know where you find those. lol This works perfectly. I was able to update the entire table in a minute.
>
>Thanks

If you say so. :) I don't see anything special about it.
As you saw, I wrote it step by step. Making it into UPDATE was simple.