How Do I Count Business or Work Days Between Two Dates?

A common business need is to count the number of business or work days between two dates. The temptation is to create a function or stored procedure that counts the days based on an algorithm. This procedural process usually involves looping though the code.

Looping through code is usually a poor choice in SQL. The best solution in SQL is to create a calendar table with each date and a date type (i.e., 0=Weekend or not worked, 1=Business, 2=Holiday). This allows you account not only for the five working days but for holidays, also. Generally, SQL will handle the table access more efficiently than it does a looping process. This solution is also simpler to implement than most procedural solutions.

Here is one possible method of implementing this solution.[ol][li]Create the calendar table:

Create Table BusinessCalendar
(BDate smalldatetime Primary Key, BType tinyint)
Go

[li]Load dates into table:

--This will handle business dates and weekends but not holidays. Change date range as needed.

Declare @dt smalldatetime
Set @dt='Jan 1 1990'
While @dt<='Dec 31 2010'
Begin
Insert BusinessCalendar Values
(@dt,
Case
When datepart(dw,@dt) Between 2 and 6
Then 1 Else 0
End)
SET @dt = @dt + 1
End

[li]Add holiday dates:

You will need to update the table to mark the holidays. You could write a script to update standard holidays or manually update the table. If you don't need to account for holidays then omit this update.

[li]Create script to count days:

After you have finished it will be easy to count business (or work) days with a simple query. This query could be included in a stored procedure or, if running SQL 2000, in a user-defined function.

Declare @startdate smalldatetime, @enddate smalldatetime
Set @startdate='dec 12 2002'
Set @enddate='jan 7 2003'

Select BDays=Count(*)
From BusinessCalendar
Where BType=1
And BDate Between @startdate And @enddate[/ol]