I have a model I wish to filter by its attribute a. The model also has another attribute b. I am trying to filter entries where a is 0 or a has the value of the b attribute (for each row, obviously). How can I filter by the value of another column?
Here is what I have tried, and the missing piece:
MyModel.objects.filter(Q(a=0) | Q(a=???)) # ??? is to be the value of the `b` column
I am using Django 1.4 and I know it is an old version that is no longer supported but unfortunately performing the upgrade is not up to me.
I think you can use an F expression with your Q object:
MyModel.objects.filter(Q(a=0) | Q(a=F('b')))
I'll also suggest you schedule your upgrade now, otherwise, you'll be missing out on other features and security fixes.
You can use the F model for comparing two fields.
from django.db.models import F
MyModel.objects.filter(a__exact = F('b'))
So for your joint query you can use something like,
MyModel.objects.filter(Q(a=0) | Q(a__exact=F('b')))