python - 没有唯一参数的唯一值错误

Question

我正在尝试使用每个Accounts唯一的用户名创建Server

class Server(models.Model):

    name = models.CharField(primary_key=True, max_length=50, unique=True)

class Account(models.Model):
    server = models.ForeignKey(Server,on_delete=models.CASCADE)
    username = models.CharField(max_length=100)
    account_name = models.CharField(max_length=100)
    password = models.CharField(max_length=50)

现在我正在
duplicate key value violates unique constraint "zuya_aaccount_username_5f0a17d4_uniq"
当我创建一个非唯一的account_name时，它没有显示任何问题

Answer 1

您可以指定 UniqueConstraint [Django-doc]来指定两个(或更多字段)在一起应该是唯一的:

class Account(models.Model):
    server = models.ForeignKey(Server,on_delete=models.CASCADE)
    username = models.CharField(max_length=100)
    account_name = models.CharField(max_length=100)
    password = models.CharField(max_length=50)

    class Meta:
        constraints = [
            models.UniqueConstraint(
                fields=['server', 'account_name'],
                name='unique_username_per_server'
            )
        ]

因此，这意味着对于同一服务器，不能存在两个具有相同Account的account_name，反之亦然。

在django-2.2之前，您可以使用 unique_together [Django-doc]元选项:

class Account(models.Model):
    server = models.ForeignKey(Server,on_delete=models.CASCADE)
    username = models.CharField(max_length=100)
    account_name = models.CharField(max_length=100)
    password = models.CharField(max_length=50)

    class Meta:
        unique_together = [['server', 'account_name']]