Product of two fields annotation

Question

I currently have a line in my Django app like this:

db.execute(\"SELECT SUM(price * qty) FROM inventory_orderline WHERE order_id = %s\", [self.id])
         


        

Answer 1

It's not clearly documented, but this can be done with the F() function:

from django.db.models import F

self.line_items.annotate(lineprice=F('orderline__price') * F('orderline__qty')).aggregate(Sum('lineprice'))