Grouping Datetime Column by Date part only.

SELECT DATEADD(dd,(DATEDIFF(dd,0,CRETS)),0), COUNT(*)
FROM Table1
GROUP BY DATEADD(dd,(DATEDIFF(dd,0,CRETS)),0)

SELECT CAST(DATEDIFF(dd,0,CRETS) AS Datetime), COUNT(*)
FROM Table1
GROUP BY CAST(DATEDIFF(dd,0,CRETS) AS Datetime)


--Don't use this:
SELECT CONVERT(Datetime, CONVERT(NCHAR(10), CRETS, 121)), COUNT(*)
FROM Table1
GROUP BY CONVERT(Datetime, CONVERT(nchar(10), CRETS, 121))

Taken from: http://www.sqldisco.com/?p=6