[Django]-Django ManyToMany filter()

by

243👍

✅

Just restating what Tomasz said.

There are many examples of FOO__in=... style filters in the many-to-many and many-to-one tests. Here is syntax for your specific problem:

users_in_1zone = User.objects.filter(zones__id=<id1>)
# same thing but using in
users_in_1zone = User.objects.filter(zones__in=[<id1>])

# filtering on a few zones, by id
users_in_zones = User.objects.filter(zones__in=[<id1>, <id2>, <id3>])
# and by zone object (object gets converted to pk under the covers)
users_in_zones = User.objects.filter(zones__in=[zone1, zone2, zone3])

The double underscore (__) syntax is used all over the place when working with querysets.

👤istruble

54👍

Note that if the user may be in multiple zones used in the query, you may probably want to add .distinct(). Otherwise you get one user multiple times:

users_in_zones = User.objects.filter(zones__in=[zone1, zone2, zone3]).distinct()
👤QB.

11👍

another way to do this is by going through the intermediate table. I’d express this within the Django ORM like this:

UserZone = User.zones.through

# for a single zone
users_in_zone = User.objects.filter(
  id__in=UserZone.objects.filter(zone=zone1).values('user'))

# for multiple zones
users_in_zones = User.objects.filter(
  id__in=UserZone.objects.filter(zone__in=[zone1, zone2, zone3]).values('user'))

it would be nice if it didn’t need the .values('user') specified, but Django (version 3.0.7) seems to need it.

the above code will end up generating SQL that looks something like:

SELECT * FROM users WHERE id IN (SELECT user_id FROM userzones WHERE zone_id IN (1,2,3))

which is nice because it doesn’t have any intermediate joins that could cause duplicate users to be returned

👤Sam Mason

2👍

You can also lookup simply by name, without __in:

class Publication(models.Model):
    ...

class Article(models.Model):
    publications = models.ManyToManyField(Publication)

Article.objects.filter(publications=1)
# or
Article.objects.filter(publications=p1)

Works with related_name as well from my tests.

per Django docs

👤egor83

1👍

I had a similar problem where some users ended with a free role and also a paid role, so I needed to select users that have two specific roles on the many to many field.

I did something like this, works like a charm

roles = [premium_role, default_role]

DiscordUser.objects.filter(guild=guild)
    .annotate(freemium=Count('roles', filter=Q(roles__in=roles)))
    .filter(freemium=2)
    .values('id')

If you want this to be more dynamic, you can change this line with

.filter(freemium=len(roles))
👤gio

0👍

You could use Q object if you have more complex query in the scenario like this question.

based on this question suppose you want to filter Users with specific id(e.g. 10) and filter Zones with the name that starts with ‘europe’

query would be like this:

filtered_zone = Q(zones__in=Zone.objects.filter(name__startswith='europe')
result = User.objects.filter(Q(id=10) & Q(filtered_zone))
👤Seyed Mostafa SeyedAshoor

Leave a comment