MySQL Function for Calculating the Working Days between 2 Dates

Lately I needed a MySQL stored function to calculate the working days (or business days) between 2 dates, however all the solutions I found online were either not configurable in terms of which week days count as working days, or really hard to read/understand. So I rolled my own, and decided to post it here in case anyone else finds it useful.

Here’s the function declaration code, as well as a usage example, hosted in GitHub (or you can find it in if it’s not showing in your browser):

The function accepts 2 dates, as well as a string that specifies which week days should count as working days. The week days are input as the integers corresponding to their WEEKDAY function representation, i.e.:

0 = Monday
1 = Tuesday
2 = Wednesday
3 = Thursday
4 = Friday
5 = Saturday
6 = Sunday

Thus if the working days are Monday to Friday, the workdays argument would be ‘01234’, and if for a more abstact example the working days are Tuesday to Thursday plus Saturday, the workdays argument would then become ‘1235’.

The function itself determines the start and end dates from the first 2 arguments (so you can use it with the earlier and later dates in any position), counts the number of whole weeks (Monday to Sunday) between the 2 dates, and then loops through the remaining days not belonging to a whole week and counts them if they are contained in the 3rd argument.

Hope you found it useful!