Incrementing values in django database

Question

I want to increment the value in the database without having to perform a hit on the db to find the actual value. Effectively, I would like to do something like this... but this does not work. Any elegant solutions?

P.objects.filter(username='John Smith').update(accvalue+=-50)

THANKS!

Answer 1

Check out Django's F() object.

You can combine it with update() method to update the value based on the previos field value i.e.

>>> from django.db.models import F
>>> P.objects.filter(username="John Smith").update(accvalue=F("accvalue") + 50)

This will use database's native UPDATE method to do what you want to do.