How do I compare two datetime fields in SQL 2005?

DECLARE  @p_date DATETIME
SET      @p_date = CONVERT( DATETIME, '14 AUG 2008 10:45:30',?)

SELECT   *
FROM     table1
WHERE    column_datetime = @p_date

@p_date=14 AUG 2008 10:45:30
column_datetime=14 AUG 2008 10:45:30

DECLARE @end datetime
SET @end = DATEADD(ss,1,@p_date)

WHERE column_datetime >= @p_date AND column_datetime < @end