T-SQL get number of working days between 2 dates

Question

I want to calculate the number of working days between 2 given dates. For example if I want to calculate the working days between 2013-01-10 and 2013-01-15, the result must

Answer 1

For stuff like this i tend to maintain a calendar table that also includes bank holidays etc.

The script i use for this is as follows (Note that i didnt write it @ i forget where i found it)

SET DATEFIRST 1
SET NOCOUNT ON
GO

--Create ISO week Function (thanks BOL)
CREATE FUNCTION ISOweek ( @DATE DATETIME )
RETURNS INT
AS 
    BEGIN
        DECLARE @ISOweek INT
        SET @ISOweek = DATEPART(wk, @DATE) + 1 - DATEPART(wk, CAST(DATEPART(yy, @DATE) AS CHAR(4)) + '0104')
        --Special cases: Jan 1-3 may belong to the previous year
        IF ( @ISOweek = 0 ) 
            SET @ISOweek = dbo.ISOweek(CAST(DATEPART(yy, @DATE) - 1 AS CHAR(4)) + '12' + CAST(24 + DATEPART(DAY, @DATE) AS CHAR(2))) + 1
        --Special case: Dec 29-31 may belong to the next year
        IF ( ( DATEPART(mm, @DATE) = 12 )
             AND ( ( DATEPART(dd, @DATE) - DATEPART(dw, @DATE) ) >= 28 )
           ) 
            SET @ISOweek = 1
        RETURN(@ISOweek)
    END
GO
--END ISOweek

--CREATE Easter algorithm function 
--Thanks to Rockmoose (http://www.sqlteam.com/forums/topic.asp?TOPIC_ID=45689)
CREATE FUNCTION fnDLA_GetEasterdate ( @year INT )
RETURNS CHAR(8)
AS 
    BEGIN
    -- Easter date algorithm of Delambre
        DECLARE @A INT ,
            @B INT ,
            @C INT ,
            @D INT ,
            @E INT ,
            @F INT ,
            @G INT ,
            @H INT ,
            @I INT ,
            @K INT ,
            @L INT ,
            @M INT ,
            @O INT ,
            @R INT              

        SET @A = @YEAR % 19
        SET @B = @YEAR / 100
        SET @C = @YEAR % 100
        SET @D = @B / 4
        SET @E = @B % 4
        SET @F = ( @B + 8 ) / 25
        SET @G = ( @B - @F + 1 ) / 3
        SET @H = ( 19 * @A + @B - @D - @G + 15 ) % 30
        SET @I = @C / 4
        SET @K = @C % 4
        SET @L = ( 32 + 2 * @E + 2 * @I - @H - @K ) % 7
        SET @M = ( @A + 11 * @H + 22 * @L ) / 451
        SET @O = 22 + @H + @L - 7 * @M

        IF @O > 31 
            BEGIN
                SET @R = @O - 31 + 400 + @YEAR * 10000
            END
        ELSE 
            BEGIN
                SET @R = @O + 300 + @YEAR * 10000
            END 

        RETURN @R
    END
GO
--END fnDLA_GetEasterdate

--Create the table
CREATE TABLE MyDateTable
    (
      FullDate DATETIME NOT NULL
                        CONSTRAINT PK_FullDate PRIMARY KEY CLUSTERED ,
      Period INT ,
      ISOWeek INT ,
      WorkingDay VARCHAR(1) CONSTRAINT DF_MyDateTable_WorkDay DEFAULT 'Y'
    )
GO
--End table create

--Populate table with required dates
DECLARE @DateFrom DATETIME ,
    @DateTo DATETIME ,
    @Period INT
SET @DateFrom = CONVERT(DATETIME, '20000101')
 --yyyymmdd (1st Jan 2000) amend as required
SET @DateTo = CONVERT(DATETIME, '20991231')
 --yyyymmdd (31st Dec 2099) amend as required
WHILE @DateFrom <= @DateTo 
    BEGIN
        SET @Period = CONVERT(INT, LEFT(CONVERT(VARCHAR(10), @DateFrom, 112), 6))
        INSERT  MyDateTable
                ( FullDate ,
                  Period ,
                  ISOWeek
                )
                SELECT  @DateFrom ,
                        @Period ,
                        dbo.ISOweek(@DateFrom)
        SET @DateFrom = DATEADD(dd, +1, @DateFrom)
    END
GO
--End population


/* Start of WorkingDays UPDATE */
UPDATE  MyDateTable
SET     WorkingDay = 'B' --B = Bank Holiday
--------------------------------EASTER---------------------------------------------
WHERE   FullDate = DATEADD(dd, -2, CONVERT(DATETIME, dbo.fnDLA_GetEasterdate(DATEPART(yy, FullDate)))) --Good Friday
        OR FullDate = DATEADD(dd, +1, CONVERT(DATETIME, dbo.fnDLA_GetEasterdate(DATEPART(yy, FullDate))))
 --Easter Monday
GO

UPDATE  MyDateTable
SET     WorkingDay = 'B'
--------------------------------NEW YEAR-------------------------------------------
WHERE   FullDate IN ( SELECT    MIN(FullDate)
                      FROM      MyDateTable
                      WHERE     DATEPART(mm, FullDate) = 1
                                AND DATEPART(dw, FullDate) NOT IN ( 6, 7 )
                      GROUP BY  DATEPART(yy, FullDate) )
---------------------MAY BANK HOLIDAYS(Always Monday)------------------------------
        OR FullDate IN ( SELECT MIN(FullDate)
                         FROM   MyDateTable
                         WHERE  DATEPART(mm, FullDate) = 5
                                AND DATEPART(dw, FullDate) = 1
                         GROUP BY DATEPART(yy, FullDate) )
        OR FullDate IN ( SELECT MAX(FullDate)
                         FROM   MyDateTable
                         WHERE  DATEPART(mm, FullDate) = 5
                                AND DATEPART(dw, FullDate) = 1
                         GROUP BY DATEPART(yy, FullDate) )
--------------------AUGUST BANK HOLIDAY(Always Monday)------------------------------
        OR FullDate IN ( SELECT MAX(FullDate)
                         FROM   MyDateTable
                         WHERE  DATEPART(mm, FullDate) = 8
                                AND DATEPART(dw, FullDate) = 1
                         GROUP BY DATEPART(yy, FullDate) )
--------------------XMAS(Move to next working day if on Sat/Sun)--------------------
        OR FullDate IN ( SELECT CASE WHEN DATEPART(dw, FullDate) IN ( 6, 7 ) THEN DATEADD(dd, +2, FullDate)
                                     ELSE FullDate
                                END
                         FROM   MyDateTable
                         WHERE  DATEPART(mm, FullDate) = 12
                                AND DATEPART(dd, FullDate) IN ( 25, 26 ) )
GO

---------------------------------------WEEKENDS--------------------------------------
UPDATE  MyDateTable
SET     WorkingDay = 'N'
WHERE   DATEPART(dw, FullDate) IN ( 6, 7 )
GO
/* End of WorkingDays UPDATE */

--SELECT * FROM MyDateTable ORDER BY 1
DROP FUNCTION fnDLA_GetEasterdate
DROP FUNCTION ISOweek
--DROP TABLE MyDateTable

SET NOCOUNT OFF

Once you have created the table, finding the number of working days is easy peasy:

SELECT  COUNT(FullDate) AS WorkingDays
FROM    dbo.tbl_WorkingDays
WHERE   WorkingDay = 'Y'
        AND FullDate >= CONVERT(DATETIME, '10/01/2013', 103)
        AND FullDate <  CONVERT(DATETIME, '15/01/2013', 103)

Note that this script includes UK bank holidays, i'm not sure what region you're in.