Django order_by sum of fields

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          


        

Answer 1

Use extra:

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