# 在ORM中设置自关联字段
class Comment(models.Model):
    user = models.ForeignKey(to='UserInfo')
    article = models.ForeignKey(to='Article')
    content = models.CharField(max_length=255)
    create_time = models.DateField(auto_now_add=True)
    parent = models.ForeignKey(to='self', null=True)

注意:自关联,关联的是当前表的主键ID字段!!!!
上表中parent对应的是Comment.pk.
切记,若关联错误,则会查询出错.