Django filter through multiple fields in a many-to-many intermediary table

问题

I have the following models in my django project:

class Video(models.Model):
    media = models.ForeignKey(Media)

class Media(models.Model):
    title = models.CharField(max_length=255)
    formats = models.ManyToManyField(Format,through='MediaFormat',related_name='media',blank=True)

class Format(models.Model):
    title = models.CharField(max_length=50)

class MediaFormat(models.Model):
    status = models.IntegerField()
    format = models.ForeignKey(Format)
    media = models.ForeignKey(Media)

Now, I want to filter all videos which have a specific format, AND the status code for that format is 10 (ready to use). How can I do that? (assuming that f is the format):

f = Format.objects.get(pk=3)

I'm tempted to use:

Video.objects.filter(media__formats=f, media__mediaformat__status=10)

But then, that would return all videos that matches both of these assumptions:

a) contain that specific format, and
b) contain any format with the status of 10

How am I supposed to filter only those who have that specific format in a status code of 10?

thank you!

回答1:

Now, I want to filter all videos which have a specific format, AND the status code for that format is 10 (ready to use). How can I do that? (assuming that f is the format)

The code you posted will do exactly what you want:

Video.objects.filter(media__formats=f, media__mediaformat__status=10)

This is documented in the filter() documentation:

Multiple parameters are joined via AND in the underlying SQL statement.

回答2:

You can chain the filters together for an "AND" construct.

Videos where the format is f AND the format's status is 10

Video.objects.filter(media__formats=f).filter(media__mediaformat__status=10)

回答3:

Probably not relevant for the OP, but might be for others like me who found this thread while searching for the right answer.

Ludwik got it right, but the section in the documentation that explains all of this, as well as how to do excludes, is in the queries documentation.

Note that splitting the filter into two filter calls like Chris suggested will give you the exact opposite result: it will search for a video that has a media format f and that has a media format, not necessarily the same media format, with a status of 10.

来源：https://stackoverflow.com/questions/5489618/django-filter-through-multiple-fields-in-a-many-to-many-intermediary-table

标签

django

many-to-many

django-orm