通过计算多行的总和来验证Django模型数据

I have two models:

我有两个型号:

class User(models.Model):
    name = models.CharField(max_length=32)


class Referral(models.Model):
    referring_user = models.ForeignKey(User, related_name="referrals")
    referred_user  = models.ForeignKey(User, related_name="referrers")
    percentage     = models.PositiveIntegerField()
class User(model