Greetings,
I have two tables: Student and Grade in a one to many relationship.
The Grade table has a field named "grade" which has integers from 0 to
5.
I want to count how many grades of each type each Student has. For
this I'm using a query similar to:
Students.objects.order_by('grades__grade').annotate(n=Count('grades'))
This SQL query does a group by Student.id and Grade.grade and orders
the results by Grade.grade. The result set is something like:
student1 2
student2 4
student3 6
student2 5
student1 3
student2 4
student3 7
As you can see there is no way of telling what grade the count was
for. What I would like is something more like:
student1 2 2
student2 4 2
student3 6 3
student2 5 3
student1 3 4
student2 4 4
student3 7 4
This means I would like somehow to add to the results the column used
in the group by statement.
A hack-ish solution is to use this query instead:
Students.objects.order_by('grades__grade').annotate(n=Count
('grades')).annotate(g=Avg('grades'))
but it doesn't feel right. I've also tried to do a .values
('grades_grade') but values() doesn't seem to work across relations.
Is there a better way to do this using the ORM?
Thanks
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