Django ManyToMany filter

Question

I have a model   class Zone models Model       name   models CharField max length 128      users   models ManyToManyField User  related name  zones   null True  blank True    And I need to contruct a filter along the lines of   u   User objects filter    zones contains a particular zone       It has to be a filter on User and it has to be a single filter parameter  The reason for this is that I am constructing a URL querystring to filter the admin user changelist  http   myserver admin auth user  zones 3  It seems like it should be simple but my brain isn t cooperating

User · Answer

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

User · Answer

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

User · Answer

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  lt id1 gt     same thing but using in users in 1zone   User objects filter zones  in   lt id1 gt       filtering on a few zones  by id users in zones   User objects filter zones  in   lt id1 gt    lt id2 gt    lt id3 gt      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

[django] Django ManyToMany filter()

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