I have a table called groups. I want to return the group number that only John and Mary are part of.
Think of a chat app, I want to see if these two existing people already have a group with ONLY them.
Group | user
1 | john
1 | mary
1 | dave
2 | john
2 | mary
How can I do this?
Here is the actual model
class Conversation(models.Model):
attendee = models.ManyToManyField(User)
guid = models.CharField(max_length=16)
An asnwer based on @arocks's approach, since @rocks's annotation is wrong.
Conversation.objects.annotate(user_count=Count('attendee')).filter(user_count=2, attendee__username="john").filter(attendee__username="mary")
That will return you a QuerySet of Conversation objects which have 2 members and members are mary and john
The reason you must you 2 separate filter is, your database management system need to create temporary subtables since you need to use same database column username twice for filtering. Your data