LISTING 1: Creation Script for the fn_workdays() Function

CREATE FUNCTION dbo.fn_workdays(@d1 AS 
datetime, @d2 AS datetime)
  RETURNS int
AS
BEGIN
  DECLARE @n AS int, @d AS datetime
  SELECT @n = 0, @d = @d1
  WHILE @d <= @d2
  BEGIN
    IF DATEPART(weekday, @d /* +@@DATEFIRST
 */) NOT IN(1, 7)
      SET @n = @n + 1
    SET @d = @d + 1
  END
  RETURN @n
END