具有复合键的模型之间的关系

Question

我有两个带有复合键的模型：

class ContestUser(models.Model):
    user_id = models.IntegerField(primary_key = True)
    contest_id = models.IntegerField(primary_key = True)
    username = models.CharField(max_length = 1536, blank = True)
    .
    .
    .



class ContestRegistration(models.Model):
    user_id = models.IntegerField(primary_key = True)
    contest_id = models.IntegerField(primary_key = True)
    status = models.IntegerField(choices = EJUDGE_CONTEST_STATUSES)
    .
    .
    .

第一个问题是如何将它们关联起来，并像连接中那样进行查询。

Select * from ContestRegistration r join ContestUser u on r.user_id = u.user_id and r.contest_id = u.contest_id where r.contest_id = 3;

其次是如何保存这样的对象？

cuser = ContestUser.objects.get(user_id = 1, contest_id = 1)
cuser.username = 'username'
cuser.save()

这会导致 IntegrityError: (1062, "Duplicate entry '1-1' for key 'PRIMARY'")

执行的 SQL 是：

SELECT * FROM `users` WHERE (`users`.`contest_id` = 1  AND `users`.`user_id` = 1 );
SELECT (1) AS `a` FROM `users` WHERE `users`.`user_id` = 1  LIMIT 1;
UPDATE `users` SET ... WHERE `users`.`user_id` = 1 ;

Answer 1

Django 模型不支持多个主键： https://docs.djangoproject.com/en/1.3/faq/models/#do-django-models-support-multiple-column-primary-keys

但是，正如文档所述，您可以在外键字段上使用其他属性，例如 unique_together 来执行相同的操作。希望对您有所帮助。