Calculate business hours between two dates

Question

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 weekda

Answer 1

An alternative solution from @Pavanred's, coming at things from a more data-based angle:

Create a table with all the dates you want to consider in it. For each day, set a number of working hours, like so:

WorkingDate Hours Comment
=========== ===== ==================
 1 Jan 2011     0 Saturday
 2 Jan 2011     0 Sunday
 3 Jan 2011     0 Public Holiday
 4 Jan 2011     8 Normal working day
 5 Jan 2011     8 Normal working day

 -- and so on, for all the days you want to report on.

This will take a small amount of setting up -- you can pre-populate it for weeks versus weekends automatically, then adjust for public holidays, etc, as necessary.

But, what you lose in the setting up, you gain in ease of querying:

SELECT
  SUM(Hours) 
FROM
  working_days 
WHERE
  WorkingDate BETWEEN @StartDate AND @EndDate

...and this can work out as an easier approach if you need to start adding more complicated rules for what defines a working day, or if your working hours vary depending on the day, etc.

It also makes the rules more easily "editable", as you don't need to change any actual code to change the definitions of a working day, add public holidays, etc.

Answer 2

A version I wrote today taking into account bank holidays. Note: This is not thoroughly tested and could no doubt be improved.

CREATE FUNCTION [dbo].[WorkingHoursBetween2Dates]
(
    @dtFrom datetime,
    @dtTo datetime
)
RETURNS INT
BEGIN
    DECLARE @tblDates AS TABLE (DateValue DATE)
    DECLARE @dFrom date = @dtFrom
    DECLARE @dTo date = @dtTo
    DECLARE @intDays int
    DECLARE @intHours int = 0
    DECLARE @dFromWorkday bit = CASE WHEN (DATENAME(WEEKDAY, @dFrom) IN ('Saturday','Sunday')) OR EXISTS (SELECT * FROM dbo.BankHolidays WHERE BankHolidayDate = @dFrom) THEN 0 ELSE 1 END
    DECLARE @dToWorkday bit = CASE WHEN (DATENAME(WEEKDAY, @dTo) IN ('Saturday','Sunday')) OR EXISTS (SELECT * FROM dbo.BankHolidays WHERE BankHolidayDate = @dTo) THEN 0 ELSE 1 END



    IF DATEPART(HOUR,@dtFrom) < 9
        SET @dtFrom = DATEADD(HOUR,9,CAST(CAST(@dtFrom AS DATE) AS DATETIME))
    ELSE
        IF DATEPART(HOUR,@dtFrom) > 17
            SET @dtFrom = DATEADD(HOUR,17,CAST(CAST(@dtFrom AS DATE) AS DATETIME))

    IF DATEPART(HOUR,@dtTo) < 9
        SET @dtTo = DATEADD(HOUR,9,CAST(CAST(@dtTo AS DATE) AS DATETIME))
    ELSE
        IF DATEPART(HOUR,@dtTo) > 17
            SET @dtTo = DATEADD(HOUR,17,CAST(CAST(@dtTo AS DATE) AS DATETIME))



    WHILE @dFrom <= @dTo
    BEGIN
        INSERT INTO @tblDates
        (
            DateValue
        )
            SELECT @dFrom
            WHERE NOT ((DATENAME(WEEKDAY, @dFrom) IN ('Saturday','Sunday')) OR EXISTS (SELECT * FROM dbo.BankHolidays WHERE BankHolidayDate = @dFrom))
        
        SET @dFrom = DATEADD(DAY,1,@dFrom)
    END
    
    SET @intDays = CASE WHEN EXISTS(SELECT * FROM @tblDates) THEN (SELECT COUNT(*) FROM @tblDates) - 1 ELSE 0 END

    IF @intDays = 0
        BEGIN
            IF @dFromWorkday = 1
                IF DATEPART(HOUR,@dtFrom) < 17
                    BEGIN
                        IF DATEDIFF(DAY,@dtFrom,@dtTo)=0
                            SET @intHours = DATEDIFF(HOUR,@dtFrom,@dtTo)
                        ELSE
                            SET @intHours = DATEDIFF(HOUR,@dtFrom,DATEADD(HOUR,17,CAST(CAST(@dtFrom AS DATE) AS DATETIME)))
                    END

            IF @dToWorkday = 1 AND DATEDIFF(DAY,@dtFrom,@dtTo)<>0
                IF DATEPART(HOUR,@dtTo) >= 17
                    SET @intHours = @intHours + 8
                ELSE
                    IF DATEPART(HOUR,@dtTo) > 9
                        SET @intHours = @intHours + DATEPART(HOUR,@dtTo) - 9
        END
    ELSE
        BEGIN
            IF @dFromWorkday = 1
                IF DATEPART(HOUR,@dtFrom) < 17
                    BEGIN
                        SET @intHours = DATEDIFF(HOUR,@dtFrom,DATEADD(HOUR,17,CAST(CAST(@dtFrom AS DATE) AS DATETIME)))
                        SET @intDays = @intDays - 1
                    END

            IF DATEPART(HOUR,@dtTo) < 17
                SET @intHours = @intHours + (@intDays * 8) + CASE WHEN @dToWorkday = 1 THEN DATEDIFF(HOUR,DATEADD(HOUR,9,CAST(CAST(@dtTo AS DATE) AS DATETIME)), @dtTo) ELSE 0 END
            ELSE
                SET @intHours = @intHours + ((@intDays + 1) * 8)
        END

    RETURN (@intHours)
END