Count work days between two dates

Question

How can I calculate the number of work days between two dates in SQL Server?

Monday to Friday and it must be T-SQL.

Answer 1

My version of the accepted answer as a function using DATEPART, so I don't have to do a string comparison on the line with

DATENAME(dw, @StartDate) = 'Sunday'

Anyway, here's my business datediff function

SET ANSI_NULLS ON
GO
SET QUOTED_IDENTIFIER ON
GO

CREATE FUNCTION BDATEDIFF
(
    @startdate as DATETIME,
    @enddate as DATETIME
)
RETURNS INT
AS
BEGIN
    DECLARE @res int

SET @res = (DATEDIFF(dd, @startdate, @enddate) + 1)
    -(DATEDIFF(wk, @startdate, @enddate) * 2)
    -(CASE WHEN DATEPART(dw, @startdate) = 1 THEN 1 ELSE 0 END)
    -(CASE WHEN DATEPART(dw, @enddate) = 7 THEN 1 ELSE 0 END)

    RETURN @res
END
GO