python - 使用 Django ORM 查询如何注释是否存在多个级别的外键层次结构

Question

我的 Django 模型看起来像

class Parent(models.Model):
    name = models.CharField(('name'), max_length=30)

class Child(models.Model):
    parent = models.ForeignKey(Parent)
    name = models.CharField(('name'), max_length=30)

class GrandChild(models.Model):
    child = models.ForeignKey(Child)
    name = models.CharField(('name'), max_length=30)

-> To Get Number of Childs for parent following query does               
    Parent.objects.annotate(childs=Count('Child')).values('childs')

-> To Get Number of Grand Childs for parent following query does               
    Parent.objects.annotate(childs=Count('child')).annotate(grandchilds=Count('child__grandchild'))

但是我怎样才能获得每个 parent 的 child 数量和孙 child 数量

Answer 1

尝试使用distinct:

Count('child', distinct=True)

通过链接了解更多详细信息:

https://docs.djangoproject.com/en/1.9/topics/db/aggregation/#combining-multiple-aggregations