Calculate business hours between two dates

How can I calculate business hours between two dates? For example we have two dates; 01/01/2010 15:00 and 04/01/2010 12:00 And we have working hours 09:00 to 17:00 in weekdays How can I calculate working hours with sql?

Answer

Baran’s answer fixed and modified for SQL 2005

SQL 2008 and above:

-- =============================================
-- Author:      Baran Kaynak (modified by Kodak 2012-04-18)
-- Create date: 14.03.2011
-- Description: 09:30 ile 17:30 arasındaki iş saatlerini hafta sonlarını almayarak toplar.
-- =============================================
CREATE FUNCTION [dbo].[WorkTime] 
(
    @StartDate DATETIME,
    @FinishDate DATETIME
)
RETURNS BIGINT
AS
BEGIN
    DECLARE @Temp BIGINT
    SET @Temp=0

    DECLARE @FirstDay DATE
    SET @FirstDay = CONVERT(DATE, @StartDate, 112)

    DECLARE @LastDay DATE
    SET @LastDay = CONVERT(DATE, @FinishDate, 112)

    DECLARE @StartTime TIME
    SET @StartTime = CONVERT(TIME, @StartDate)

    DECLARE @FinishTime TIME
    SET @FinishTime = CONVERT(TIME, @FinishDate)

    DECLARE @WorkStart TIME
    SET @WorkStart = '09:00'

    DECLARE @WorkFinish TIME
    SET @WorkFinish = '17:00'

    DECLARE @DailyWorkTime BIGINT
    SET @DailyWorkTime = DATEDIFF(MINUTE, @WorkStart, @WorkFinish)

    IF (@StartTime<@WorkStart)
    BEGIN
        SET @StartTime = @WorkStart
    END
    IF (@FinishTime>@WorkFinish)
    BEGIN
        SET @FinishTime=@WorkFinish
    END
    IF (@FinishTime<@WorkStart)
    BEGIN
        SET @FinishTime=@WorkStart
    END
    IF (@StartTime>@WorkFinish)
    BEGIN
        SET @StartTime = @WorkFinish
    END

    DECLARE @CurrentDate DATE
    SET @CurrentDate = @FirstDay
    DECLARE @LastDate DATE
    SET @LastDate = @LastDay

    WHILE(@CurrentDate<=@LastDate)
    BEGIN       
        IF (DATEPART(dw, @CurrentDate)!=1 AND DATEPART(dw, @CurrentDate)!=7)
        BEGIN
            IF (@CurrentDate!=@FirstDay) AND (@CurrentDate!=@LastDay)
            BEGIN
                SET @Temp = @Temp + @DailyWorkTime
            END
            --IF it starts at startdate and it finishes not this date find diff between work finish and start as minutes
            ELSE IF (@CurrentDate=@FirstDay) AND (@CurrentDate!=@LastDay)
            BEGIN
                SET @Temp = @Temp + DATEDIFF(MINUTE, @StartTime, @WorkFinish)
            END

            ELSE IF (@CurrentDate!=@FirstDay) AND (@CurrentDate=@LastDay)
            BEGIN
                SET @Temp = @Temp + DATEDIFF(MINUTE, @WorkStart, @FinishTime)
            END
            --IF it starts and finishes in the same date
            ELSE IF (@CurrentDate=@FirstDay) AND (@CurrentDate=@LastDay)
            BEGIN
                SET @Temp = DATEDIFF(MINUTE, @StartTime, @FinishTime)
            END
        END
        SET @CurrentDate = DATEADD(day, 1, @CurrentDate)
    END

    -- Return the result of the function
    IF @Temp<0
    BEGIN
        SET @Temp=0
    END
    RETURN @Temp

END

SQL 2005 and below:

-- =============================================
-- Author:      Baran Kaynak (modified by Kodak 2012-04-18)
-- Create date: 14.03.2011
-- Description: 09:30 ile 17:30 arasındaki iş saatlerini hafta sonlarını almayarak toplar.
-- =============================================
CREATE FUNCTION [dbo].[WorkTime] 
(
    @StartDate DATETIME,
    @FinishDate DATETIME
)
RETURNS BIGINT
AS
BEGIN
    DECLARE @Temp BIGINT
    SET @Temp=0

    DECLARE @FirstDay DATETIME
    SET @FirstDay = DATEADD(dd, 0, DATEDIFF(dd, 0, @StartDate))

    DECLARE @LastDay DATETIME
    SET @LastDay = DATEADD(dd, 0, DATEDIFF(dd, 0, @FinishDate))

    DECLARE @StartTime DATETIME
    SET @StartTime = @StartDate - DATEADD(dd, DATEDIFF(dd, 0, @StartDate), 0)

    DECLARE @FinishTime DATETIME
    SET @FinishTime = @FinishDate - DATEADD(dd, DATEDIFF(dd, 0, @FinishDate), 0)

    DECLARE @WorkStart DATETIME
    SET @WorkStart = CONVERT(DATETIME, '09:00', 8)

    DECLARE @WorkFinish DATETIME
    SET @WorkFinish = CONVERT(DATETIME, '17:00', 8)

    DECLARE @DailyWorkTime BIGINT
    SET @DailyWorkTime = DATEDIFF(MINUTE, @WorkStart, @WorkFinish)

    IF (@StartTime<@WorkStart)
    BEGIN
        SET @StartTime = @WorkStart
    END
    IF (@FinishTime>@WorkFinish)
    BEGIN
        SET @FinishTime=@WorkFinish
    END
    IF (@FinishTime<@WorkStart)
    BEGIN
        SET @FinishTime=@WorkStart
    END
    IF (@StartTime>@WorkFinish)
    BEGIN
        SET @StartTime = @WorkFinish
    END

    DECLARE @CurrentDate DATETIME
    SET @CurrentDate = @FirstDay
    DECLARE @LastDate DATETIME
    SET @LastDate = @LastDay

    WHILE(@CurrentDate<=@LastDate)
    BEGIN       
        IF (DATEPART(dw, @CurrentDate)!=1 AND DATEPART(dw, @CurrentDate)!=7)
        BEGIN
            IF (@CurrentDate!=@FirstDay) AND (@CurrentDate!=@LastDay)
            BEGIN
                SET @Temp = @Temp + @DailyWorkTime
            END
            --IF it starts at startdate and it finishes not this date find diff between work finish and start as minutes
            ELSE IF (@CurrentDate=@FirstDay) AND (@CurrentDate!=@LastDay)
            BEGIN
                SET @Temp = @Temp + DATEDIFF(MINUTE, @StartTime, @WorkFinish)
            END

            ELSE IF (@CurrentDate!=@FirstDay) AND (@CurrentDate=@LastDay)
            BEGIN
                SET @Temp = @Temp + DATEDIFF(MINUTE, @WorkStart, @FinishTime)
            END
            --IF it starts and finishes in the same date
            ELSE IF (@CurrentDate=@FirstDay) AND (@CurrentDate=@LastDay)
            BEGIN
                SET @Temp = DATEDIFF(MINUTE, @StartTime, @FinishTime)
            END
        END
        SET @CurrentDate = DATEADD(day, 1, @CurrentDate)
    END

    -- Return the result of the function
    IF @Temp<0
    BEGIN
        SET @Temp=0
    END
    RETURN @Temp

END