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

If you need to add work days to a given date, you can create a function that depends on a calendar table, described below:

CREATE TABLE Calendar
(
  dt SMALLDATETIME PRIMARY KEY, 
  IsWorkDay BIT
);

--fill the rows with normal days, weekends and holidays.


create function AddWorkingDays (@initialDate smalldatetime, @numberOfDays int)
    returns smalldatetime as 

    begin
        declare @result smalldatetime
        set @result = 
        (
            select t.dt from
            (
                select dt, ROW_NUMBER() over (order by dt) as daysAhead from calendar 
                where dt > @initialDate
                and IsWorkDay = 1
                ) t
            where t.daysAhead = @numberOfDays
        )

        return @result
    end