How can I calculate the number of work days between two dates in SQL Server?
Monday to Friday and it must be T-SQL.
Here is a version that works well (I think). Holiday table contains Holiday_date columns that contains holidays your company observe.
DECLARE @RAWDAYS INT
SELECT @RAWDAYS = DATEDIFF(day, @StartDate, @EndDate )--+1
-( 2 * DATEDIFF( week, @StartDate, @EndDate ) )
+ CASE WHEN DATENAME(dw, @StartDate) = 'Saturday' THEN 1 ELSE 0 END
- CASE WHEN DATENAME(dw, @EndDate) = 'Saturday' THEN 1 ELSE 0 END
SELECT @RAWDAYS - COUNT(*)
FROM HOLIDAY NumberOfBusinessDays
WHERE [Holiday_Date] BETWEEN @StartDate+1 AND @EndDate
In Calculating Work Days you can find a good article about this subject, but as you can see it is not that advanced.
--Changing current database to the Master database allows function to be shared by everyone.
USE MASTER
GO
--If the function already exists, drop it.
IF EXISTS
(
SELECT *
FROM dbo.SYSOBJECTS
WHERE ID = OBJECT_ID(N'[dbo].[fn_WorkDays]')
AND XType IN (N'FN', N'IF', N'TF')
)
DROP FUNCTION [dbo].[fn_WorkDays]
GO
CREATE FUNCTION dbo.fn_WorkDays
--Presets
--Define the input parameters (OK if reversed by mistake).
(
@StartDate DATETIME,
@EndDate DATETIME = NULL --@EndDate replaced by @StartDate when DEFAULTed
)
--Define the output data type.
RETURNS INT
AS
--Calculate the RETURN of the function.
BEGIN
--Declare local variables
--Temporarily holds @EndDate during date reversal.
DECLARE @Swap DATETIME
--If the Start Date is null, return a NULL and exit.
IF @StartDate IS NULL
RETURN NULL
--If the End Date is null, populate with Start Date value so will have two dates (required by DATEDIFF below).
IF @EndDate IS NULL
SELECT @EndDate = @StartDate
--Strip the time element from both dates (just to be safe) by converting to whole days and back to a date.
--Usually faster than CONVERT.
--0 is a date (01/01/1900 00:00:00.000)
SELECT @StartDate = DATEADD(dd,DATEDIFF(dd,0,@StartDate), 0),
@EndDate = DATEADD(dd,DATEDIFF(dd,0,@EndDate) , 0)
--If the inputs are in the wrong order, reverse them.
IF @StartDate > @EndDate
SELECT @Swap = @EndDate,
@EndDate = @StartDate,
@StartDate = @Swap
--Calculate and return the number of workdays using the input parameters.
--This is the meat of the function.
--This is really just one formula with a couple of parts that are listed on separate lines for documentation purposes.
RETURN (
SELECT
--Start with total number of days including weekends
(DATEDIFF(dd,@StartDate, @EndDate)+1)
--Subtact 2 days for each full weekend
-(DATEDIFF(wk,@StartDate, @EndDate)*2)
--If StartDate is a Sunday, Subtract 1
-(CASE WHEN DATENAME(dw, @StartDate) = 'Sunday'
THEN 1
ELSE 0
END)
--If EndDate is a Saturday, Subtract 1
-(CASE WHEN DATENAME(dw, @EndDate) = 'Saturday'
THEN 1
ELSE 0
END)
)
END
GO
If you need to use a custom calendar, you might need to add some checks and some parameters. Hopefully it will provide a good starting point.
Create Function dbo.DateDiff_WeekDays
(
@StartDate DateTime,
@EndDate DateTime
)
Returns Int
As
Begin
Declare @Result Int = 0
While @StartDate <= @EndDate
Begin
If DateName(DW, @StartDate) not in ('Saturday','Sunday')
Begin
Set @Result = @Result +1
End
Set @StartDate = DateAdd(Day, +1, @StartDate)
End
Return @Result
End
This is basically CMS's answer without the reliance on a particular language setting. And since we're shooting for generic, that means it should work for all @@datefirst
settings as well.
datediff(day, <start>, <end>) + 1 - datediff(week, <start>, <end>) * 2
/* if start is a Sunday, adjust by -1 */
+ case when datepart(weekday, <start>) = 8 - @@datefirst then -1 else 0 end
/* if end is a Saturday, adjust by -1 */
+ case when datepart(weekday, <end>) = (13 - @@datefirst) % 7 + 1 then -1 else 0 end
datediff(week, ...)
always uses a Saturday-to-Sunday boundary for weeks, so that expression is deterministic and doesn't need to be modified (as long as our definition of weekdays is consistently Monday through Friday.) Day numbering does vary according to the @@datefirst
setting and the modified calculations handle this correction with the small complication of some modular arithmetic.
A cleaner way to deal with the Saturday/Sunday thing is to translate the dates prior to extracting a day of week value. After shifting, the values will be back in line with a fixed (and probably more familiar) numbering that starts with 1 on Sunday and ends with 7 on Saturday.
datediff(day, <start>, <end>) + 1 - datediff(week, <start>, <end>) * 2
+ case when datepart(weekday, dateadd(day, @@datefirst, <start>)) = 1 then -1 else 0 end
+ case when datepart(weekday, dateadd(day, @@datefirst, <end>)) = 7 then -1 else 0 end
I've tracked this form of the solution back at least as far as 2002 and an Itzik Ben-Gan article. (https://technet.microsoft.com/en-us/library/aa175781(v=sql.80).aspx) Though it needed a small tweak since newer date
types don't allow date arithmetic, it is otherwise identical.
EDIT:
I added back the +1
that had somehow been left off. It's also worth noting that this method always counts the start and end days. It also assumes that the end date is on or after the start date.
DECLARE @StartDate datetime,@EndDate datetime
select @StartDate='3/2/2010', @EndDate='3/7/2010'
DECLARE @TotalDays INT,@WorkDays INT
DECLARE @ReducedDayswithEndDate INT
DECLARE @WeekPart INT
DECLARE @DatePart INT
SET @TotalDays= DATEDIFF(day, @StartDate, @EndDate) +1
SELECT @ReducedDayswithEndDate = CASE DATENAME(weekday, @EndDate)
WHEN 'Saturday' THEN 1
WHEN 'Sunday' THEN 2
ELSE 0 END
SET @TotalDays=@TotalDays-@ReducedDayswithEndDate
SET @WeekPart=@TotalDays/7;
SET @DatePart=@TotalDays%7;
SET @WorkDays=(@WeekPart*5)+@DatePart
SELECT @WorkDays
I took the various examples here, but in my particular situation we have a @PromisedDate for delivery and a @ReceivedDate for the actual receipt of the item. When an item was received before the "PromisedDate" the calculations were not totaling correctly unless I ordered the dates passed into the function by calendar order. Not wanting to check the dates every time, I changed the function to handle this for me.
Create FUNCTION [dbo].[fnGetBusinessDays]
(
@PromiseDate date,
@ReceivedDate date
)
RETURNS integer
AS
BEGIN
DECLARE @days integer
SELECT @days =
Case when @PromiseDate > @ReceivedDate Then
DATEDIFF(d,@PromiseDate,@ReceivedDate) +
ABS(DATEDIFF(wk,@PromiseDate,@ReceivedDate)) * 2 +
CASE
WHEN DATENAME(dw, @PromiseDate) <> 'Saturday' AND DATENAME(dw, @ReceivedDate) = 'Saturday' THEN 1
WHEN DATENAME(dw, @PromiseDate) = 'Saturday' AND DATENAME(dw, @ReceivedDate) <> 'Saturday' THEN -1
ELSE 0
END +
(Select COUNT(*) FROM CompanyHolidays
WHERE HolidayDate BETWEEN @ReceivedDate AND @PromiseDate
AND DATENAME(dw, HolidayDate) <> 'Saturday' AND DATENAME(dw, HolidayDate) <> 'Sunday')
Else
DATEDIFF(d,@PromiseDate,@ReceivedDate) -
ABS(DATEDIFF(wk,@PromiseDate,@ReceivedDate)) * 2 -
CASE
WHEN DATENAME(dw, @PromiseDate) <> 'Saturday' AND DATENAME(dw, @ReceivedDate) = 'Saturday' THEN 1
WHEN DATENAME(dw, @PromiseDate) = 'Saturday' AND DATENAME(dw, @ReceivedDate) <> 'Saturday' THEN -1
ELSE 0
END -
(Select COUNT(*) FROM CompanyHolidays
WHERE HolidayDate BETWEEN @PromiseDate and @ReceivedDate
AND DATENAME(dw, HolidayDate) <> 'Saturday' AND DATENAME(dw, HolidayDate) <> 'Sunday')
End
RETURN (@days)
END