Django Aggregation: Summation of Multiplication of two fields
django, django-models, django-orm, django-queryset, python
Solution
Update: for Django >= 1.8 please follow the answer provided by @kmmbvnr
it's possible using Django ORM:
here's what you should do:
from django.db.models import Sum
total = ( Task.objects
.filter(your-filter-here)
.aggregate(
total=Sum('progress', field="progress*estimated_days")
)['total']
)
Note: if the two fields are of different types, say `integer` & `float`, the type you want to return should be passed as the first parameter of `Sum`
It's a late answer, but I guess it'll help someone looking for the same.
Problem
I have a model something like this: ``` class Task(models.Model): progress = models.PositiveIntegerField() estimated_days = models.PositiveIntegerField() ``` Now I would like to do a calculation `Sum(progress * estimated_days)` on the database level. Using Django Aggregation I can have the sum for each field but not the summation of multiplication of fields.