如何查询除已经在另一个模型中的模型对象之外的所有模型对象？

Question

我正在开发 Django 应用程序。我有 2 个与问题相关的模型：

class Quiz(models.Model):
  """
  Represents a Quiz for a `Module`.

  It will have a `name`
  """
  name = models.CharField(max_length=200)
  user = models.ManyToManyField('cme.Bussines', related_name='quizes', through='UserQuiz', through_fields=('quiz', 'user'))

  def __str__(self) -> str:
    return f'{self.name}'

class Trio(models.Model):
  """
  Represents the content for a Module.  

  Each `Trio` will have, as it's name says, 3 content fields, plus the
  `Module` it belongs to.

  It will have a `file`, a `video` (which will be a URL to a YT video), and a `quiz`
  (which will be key to `Quiz`)
  """
  file = models.FileField(upload_to='legacy/classes/', max_length=254)
  quiz = models.ForeignKey(Quiz, on_delete=models.SET_NULL, related_name='trios', null=True, blank=True)
  video = models.URLField()
  module = models.ForeignKey(Module, on_delete=models.CASCADE, related_name='trios')
  user = models.ManyToManyField('cme.Bussines', related_name='trios', through='UserTrio', through_fields=('trio', 'user'))

  def __str__(self) -> str:
    return f'Trio {self.id} de {self.module}'

我想查询不在Trio的quiz字段中的所有Quizzes。有办法吗？

Answer 1

是的，您可以查询：

Quiz.objects.filter(<strong>trios=None</strong>)

这将创建一个 LEFT OUTER JOIN 并且只保留 Quizzes 没有相关的 Trio 对象。

Answer 2

您可以查询在任何 Trio 对象中看到其 id 的所有 Quiz 对象：

Quiz.objects.exclude(id__in=Trio.objects.values("quiz_id"))

您还可以进一步优化查询。例如，假设您想要所有 Quiz 对象未被 Trio 对象的特定子集引用，您可以通过在排除表达式中添加过滤器来实现，类似于：

Quiz.objects.exclude(id__in=Trio.objects.filter(...).values("quiz_id"))

如何查询除已经在另一个模型中的模型对象之外的所有模型对象？

How to query all model objects except the ones that already are in another model?

python

django

django-models