Get the date portion of a datetime for sql server 2000

Using T-SQL in SQL Server 2000 you sometimes want compare a given datetime value with date by ignoring the time portion of the datetime value.

Here are three ways to strip off the time which gives the following:
2007-06-21 11:23:41.321 => 2007-06-21 00:00:00.000

1) convert to string in format (ISO yymmdd), then cast to datetime
- select on 500000 items takes 1703 ms

SELECT CAST( CONVERT( CHAR(8), GetDate(), 112) AS DATETIME)

2) convert to number of days in float, cut all that is smaller than a day, then cast to datetime
- select on 500000 items takes 228 ms

SELECT CAST( FLOOR( CAST( GETDATE() AS FLOAT ) ) AS DATETIME )

3) get the difference form zero date as number of days, then add this number to zero date.
- select on 500000 items takes 184 ms

SELECT DATEADD(d, 0, DATEDIFF(d, 0, GETDATE()))

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Performance tested like this.

SET DATEFORMAT dmy
SET STATISTICS IO ON
SET STATISTICS TIME ON
select myDateTime
from #dummy
where CAST( FLOOR( CAST( myDateTime AS FLOAT ) ) AS DATETIME ) = '02/07/2007'
SET STATISTICS TIME OFF
SET STATISTICS IO OFF