Annotating a Sum results in None rather than zero

Question

I\'m making a QA site that is similar to the page you\'re on right now. I\'m attempting to order answers by their score, but answers which have no votes are having their score

Answer 1

You can use the Coalesce function from django.db.models.functions like:

answers = (Answer.objects
    .filter(<something here>)
    .annotate(score=Coalesce(Sum('vote__type'), 0))
    .order_by('-score'))

Answer 2

What about you use custom Manager? For example:

AnswerManager(models.Manager):
    def all_with_score(self):
       qs = self.get_query_set().annotate(score=Sum('vote__type'))
       # Here, you can do stuff with QuerySet, for example
       # iterate over all Answers and set 'score' to zero if None.

Answer(models.Model):
    //some fields here
    objects = AnswerManager()

Then, you can use:

>>> answers = Answer.objects.all_with_score().order_by('-score')