python 多对一

多对一关系 :

Django 使用django.db.models.ForeignKey 定义多对一关系,和使用其他字段类型一样,在模型当中把它作为一个类属性包含进来。


ForeignKey 需要一个位置参数：与该模型关联的类。


class Question(models.Model):
    question_text = models.CharField(max_length=200)
    pub_date = models.DateTimeField('date published')
    def __str__(self):              # __unicode__ on Python 2
        return self.question_text


class Choice(models.Model):
    question = models.ForeignKey(Question)
    choice_text = models.CharField(max_length=200)
    votes = models.IntegerField(default=0)
    def __str__(self):              # __unicode__ on Python 2
        return self.choice_text




mysql> select * from polls_choice;
+----+-------------+-------+-------------+
| id | choice_text | votes | question_id |
+----+-------------+-------+-------------+
|  1 | 999999      |     7 |           1 |
|  2 | 88888       |     3 |           2 |
|  3 | 77777       |     6 |           1 |
+----+-------------+-------+-------------+
3 rows in set (0.00 sec)

mysql> select * from polls_question;
+----+---------------+----------------------------+
| id | question_text | pub_date                   |
+----+---------------+----------------------------+
|  1 | What's up?    | 2018-07-13 02:01:34.356621 |
|  2 | aaaaaa        | 2017-01-01 12:00:00.000000 |
|  3 | bbbbb         | 2018-07-13 02:00:00.000000 |
+----+---------------+----------------------------+
3 rows in set (0.00 sec)

http://192.168.137.3:8000/polls/1/vote/


What's up?
You didn't select a choice.

999999
77777