I am working on a Django application. I have 2 models relevant to the question:
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}'
I want to query all the Quizzes that are not in quiz field of Trio. Is there a way of doing this?
Yes, you can query with:
Quiz.objects.filter(trios=None)This will make a LEFT OUTER JOIN and only retain Quizzes for which there is no related Trio object.
You can query all Quiz objects whose id is seen in any Trio object :
Quiz.objects.exclude(id__in=Trio.objects.values("quiz_id"))
You can also refine the query further. For example, let's say you want all Quiz objects not referred by a specific subset of Trio objects, you can do so by adding a filter in your exclude expression, something like :
Quiz.objects.exclude(id__in=Trio.objects.filter(...).values("quiz_id"))