Create FUNCTION [dbo].[GetWorkDateDiff]
(
@begin_date datetime,
@days int
)
RETURNS datetime
AS
BEGIN
DECLARE @WorkDays int=1
declare @weekday Nvarchar(9)
Declare @End_Date datetime
    while (@WorkDays<@days)
      begin
        select @weekday=datename(weekday,dateadd(d,@WorkDays,@begin_date))
         if (@weekday='星期六' or  @weekday='星期日' or @weekday='Saturday' or @weekday='Sunday')
             set @days=@days+1
        set @WorkDays=@WorkDays+1
      end
    RETURN Dateadd(dd,@WorkDays,@Begin_Date)
END

DECLARE @OldDate Datetime='2012-4-24'
DECLARE @Days int=5
--直接加@Days个工作日
SELECT [dbo].[GetWorkDateDiff](@OldDate,@Days)

/*
2012-05-01 00:00:00.000
*/