[Answered ]-Django advanced queries

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I have 3 models: Pupils, Instructor, Group. They are connected through
the Pupils model like so:

This means that you have a M2M relation between Instructor and Group which you can define like this:

class Instructor:
    #...
    groups = models.ManyToManyField(Group, through='Pupils')

Now using this M2M relation, you can take an instructor groups like this:

instructor.groups.all()

you can also use the reverse relation of the M2M relation in order to get all instructors for a group.

group.instructor_set.all()

you can also get the instructors count by using .count()

#group instructors count
group.instructor_set.count()
#or if you want to count pupils, 
#use the reverse relation of the ForeignKey
#group.pupils_set.count()

Now about the 2nd part of the question if I understand it correctly you need something like this:

#this will give you instructors of a group with their pupils count.
group.instructor_set.annotate(pupils_count=Count('pupils'))
👤Todor

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