[Solved]-Django: Annotate based on an annotation

you can use query like this :

class SumSubquery(Subquery):
    template = "(SELECT SUM(`%(field)s`) From (%(subquery)s _sum))"
    output_field = models.Floatfield()
    def as_sql(self, compiler, connection, template=None, **extra_context):
        connection.ops.check_expression_support(self)
        template_params = {**self.extra, **extra_context}
        template_params['subquery'], sql_params = self.queryset.query.get_compiler(connection=connection).as_sql()
        template_params["field"] = list(self.queryset.query.annontation_select_mask)[0]
        sql = template % template_params
        return sql, sql_params



Team.objects.all().values("sport__name").annotate(variance=SumSubquery(Player.objects.filter(team__sport_id=OuterRef("sport_id")).annotate(sum_pow=ExpressionWrapper((Avg("team__players__weight") - F("weight"))**2,output_field=models.Floatfield())).values("sum_pow"))/(Count("players", output_field=models.FloatField())-1))

and add related name to model like this:

class Player(models.Model):
    name = models.CharField()
    weight = models.DecimalField()
    team = models.ForeignKey('Team', related_name="players")

I’m going to assume (perhaps incorrectly) that you mean by ‘variance’ the difference between maximum and minimum weights. If so, you can generate more than one aggregate with a single query, like so:

from django.db.models import Avg, Max, Min

Team.objects.aggregate(Avg('player__weight'), Max('player__weight'), Min('player__weight'))

This is taken from the django docs on generating aggregation over a queryset.