Let's say I have the following two models:
class Parent(models.Model):
factor = models.DecimalField(...)
... other fields
class Child(models.Model):
field_a = models.DecimalField(...)
field_b = models.DecimalField(...)
parent = models.ForeignKey(Parent)
... other fields
Now I want to calculate the sum of (field_a * field_b * factor)
of all objects in the Child
model. I can calculate the sum of (field_a * field_b)
with aggregate(value=Sum(F('field_a')*F('field_b'), output_field=DecimalField()))
. My question is how I can pull out the factor
field from the Parent
model?
I am new to Django and I really appreciate your help!
Django let's you follow relationships with the double underscore (__) as deep as you like. So in your case F('parent__factor')
should do the trick.
The full queryset:
Child.objects.aggregate(value=Sum(F('field_a') * F('field_b') * F('parent__factor'), output_field=DecimalField()))
The technical post webpages of this site follow the CC BY-SA 4.0 protocol. If you need to reprint, please indicate the site URL or the original address.Any question please contact:yoyou2525@163.com.