Django order_by 字段总和

Question

Is it possible to use the django ORM to order a queryset by the sum of two different fields?

For example, I have a model that looks like this:

class Component(models.Model):
    material_cost = CostField()
    labor_cost = CostField()

and I want to do something like this:

component = Component.objects.order_by(F('material_cost') + F('labor_cost'))[0]

But unfortunately, F objects don't seem to work with 'order_by'. Is such a thing possible with django?

Answer 1

You can use extra for this.

Component.objects.extra(
    select={'fieldsum':'material_cost + labor_cost'},
    order_by=('fieldsum',)
)

See the documentation .

Answer 2

I think it's time to provide better answer. Since django team is considering deprecating extra() , it's better to use annotate() with F() expression:

from django.db.models import F

Component.objects.annotate(fieldsum=F('material_cost') + F('labor_cost')).order_by('fieldsum')

see also https://code.djangoproject.com/ticket/25676

Answer 3

Use extra:

Component.objects.extra(select = {'total_cost' : 'material_cost + labor_cost'},
                                   order_by = ['total_cost',])[0]

Answer 4

You can use F() expression directly in order_by now, your suggested code should work:

component = Component.objects.order_by(F('material_cost') + F('labor_cost'))