T-SQL Date Difference for WeekDays only - sql-server

Question

I am trying to get the date difference in a given date excluding the week days.
Here is what I have:
SELECT DATEADD (w, -4, GETDATE())
This returns 2013-05-04 19:01:53.170, which means that it also counts weekends.
Same for
SELECT DATEADD (dw, -4, GETDATE())
Any help will be appreciated.
Thanks in advance.

Answer 1

I'm using these functions that return the non-weekend seconds between two dates:
CREATE FUNCTION [dbo].[DateDiff_NoWeekends](
#date1 DATETIME,
#date2 DATETIME
)
RETURNS INT AS BEGIN
DECLARE #retValue INT
SET #date1 = dbo.__CorrectDate(#date1, 1)
SET #date2 = dbo.__CorrectDate(#date2, 0)
IF (#date1 >= #date2)
SET #retValue = 0
ELSE BEGIN
DECLARE #days INT, #weekday INT
SET #days = DATEDIFF(d, #date1, #date2)
SET #weekday = DATEPART(dw, #date1) - 1
SET #retValue = DATEDIFF(s, #date1, #date2) - 2 * 24 * 3600 * ((#days + #weekday) / 7)
END
RETURN #retValue
END
GO
CREATE FUNCTION [dbo].[__CorrectDate](
#date DATETIME,
#forward INT
)
RETURNS DATETIME AS BEGIN
IF (DATEPART(dw, #date) > 5) BEGIN
IF (#forward = 1) BEGIN
SET #date = #date + (8 - DATEPART(dw, #date))
SET #date = DateAdd(Hour, (8 - DatePart(Hour, #date)), #date)
END ELSE BEGIN
SET #date = #date - (DATEPART(dw, #date)- 5)
SET #date = DateAdd(Hour, (18 - DatePart(Hour, #date)), #date)
END
SET #date = DateAdd(Minute, -DatePart(Minute, #date), #date)
SET #date = DateAdd(Second, -DatePart(Second, #date), #date)
END
RETURN #date
END
Here's a sql-fiddle demo for all non-weekend days in april (22).
SELECT [no weekend days in april] =
(dbo.DateDiff_NoWeekends('2013-04-01','2013-05-01')
/ 3600 / 24)

Answer 2

The query below gives the difference for week days alone , Ie counts the no od days between two days and subtracts the no of weekend days ,
DECLARE #StartDate DATETIME,
#EndDate DATETIME
SELECT #StartDate = '01-July-2008',
#EndDate = '30-July-2008'
;WITH DATE (Date1)
AS (
SELECT DATEADD(DAY, DATEDIFF(DAY, '19000101', #StartDate), '19000101')
UNION ALL
SELECT DATEADD(DAY, 1, Date1)
FROM DATE
WHERE Date1 < #EndDate
)
SELECT count(*) -
(
SELECT count(*)
--CONVERT(VARCHAR(15),d1.DATE1 ,110) as [Working Date],
--DATENAME(weekday, d1.Date1) [Working Day]
from DATE d1 where (DATENAME(weekday, d1.Date1)) in ('Saturday','Sunday')
)
--CONVERT(VARCHAR(15),d1.DATE1 ,110) as [Working Date],
--DATENAME(weekday, d1.Date1) [Working Day]
from DATE d1 where (DATENAME(weekday, d1.Date1)) not in ('Saturday','Sunday')
please let me know for any clarifications

Answer 3

Maybe I am still missing some full testing, but this works for me too: take the difference in days and then subtract 2 days for each weekend
DateDiff(d, d1, d2) - 2*DateDiff(wk, d1, d2)
Could be put in a function as well