DATEDIFF and exclude weekends

[HobbyMan]

I came up with this user defined function today.

Was wondering if someone would look at it and see if anything is wrong?

/*
* User Defined Function :: fn_Drop_Weekends
*
* In trying to find the datediff between two
* dates, there was a need to exclude the weekends.
* Thus this function. It will check each day between
* Begin/End. If there is a weekend day it will take
* one away from the ending date.
*
* EXAMPLE: Select AVG(Datediff(mi, Date0, dbo.Drop_Weekends(Date0,Date1)))/60.0
*
* PARAM 1 = Beginning Date
* PARAM 2 = Ending Date
*
* OUTPUT datetime
*/
CREATE FUNCTION fn_Drop_Weekends ( @DATE_BEGIN datetime, @DATE_END datetime )
RETURNS datetime
AS
BEGIN

DECLARE @dateB datetime
SET @dateB=@DATE_BEGIN

DECLARE @dateE datetime
SET @dateE=@DATE_END

DECLARE @returnDate datetime
SET @returnDate=@DATE_END

WHILE @dateB < @dateE
BEGIN
IF DATEPART (dw, @dateB) IN (1,7)
BEGIN
SET @returnDate = @returnDate - 1
END

SET @dateB = @dateB + 1
END
RETURN (@returnDate);
END

 

[jhall156]

It seems to me that the DATEPART for the day of the week is non-deterministic because of firstday and shouldn't work in a user defined function. I tried and seems to work. (Head scratching). JHall