SET NOCOUNT ON

DECLARE @newdate DATETIME
DECLARE @tbl TABLE ( pk int IDENTITY, dt datetime, dtp datetime)

INSERT INTO @tbl (dt) VALUES ('1/1/1900 9:10:48')
INSERT INTO @tbl (dt) VALUES ('12/21/1998 14:45:48.123')
INSERT INTO @tbl (dt) VALUES (getdate())

SET @newdate = '2005-07-13'

UPDATE @tbl 
  SET dtp = dt, 
      dt = DATEADD(dd, DATEDIFF(dd, dt, @newdate), dt)

SELECT * FROM @tbl

>DATEPART selects the part of the date to extract, as does Day, Month, and Year. Is there a way to update a datetime field so that the original is not changed except for the part that needs to be? For example, if @settime = 1/1/1900 9:10:48 AM and I wanted to update it to 7/13/2005 9:10:48 AM, is there a set-based command that would do that?