How to pass RawQuerySet result as a JSONResponse in DJango? - json

Question

I have two models like this:
class McqQuestion(models.Model):
mcq_question_id = models.IntegerField()
test_id = models.ForeignKey('exam.Test')
mcq_right_answer = models.IntegerField()
class UserMcqAnswer(models.Model):
user = models.ForeignKey('exam.UserInfo')
test_id = models.ForeignKey('exam.Test')
mcq_question_id=models.ForeignKey('exam.McqQuestion')
user_answer = models.IntegerField()
I need to match the user_answer and mcq_right_answer. Able to do that by executing the below raw query.
rightAns=UserMcqAnswer.objects.raw('SELECT B.id, COUNT(A.mcq_question_id) AS RightAns\
FROM exam_mcqquestion AS A\
LEFT JOIN exam_usermcqanswer AS B\
ON A.mcq_question_id=B.mcq_question_id_id\
WHERE B.test_id_id=%s AND B.user_id=%s AND\
A.mcq_right_answer=B.user_answer',[test_id,user_id])
1) But the problem is that couldn't able to pass the result as JSONResponse because it says TypeError: Object of type 'RawQuerySet' is not JSON serializable
2) Is there any alternative to this raw query by using the objects and filtered querysets?

Answer 1

Django's serialize function's second argument can be any iterator that yields Django model instances.
So, in principle, you can use that raw SQL query that you worked on, using something like this:
query = """SELECT B.id, COUNT(A.mcq_question_id) AS RightAns\
FROM exam_mcqquestion AS A\
LEFT JOIN exam_usermcqanswer AS B\
ON A.mcq_question_id=B.mcq_question_id_id\
WHERE B.test_id_id=%s AND B.user_id=%s AND\
A.mcq_right_answer=B.user_answer"""%(test_id, user_id)
and then getting the json data you'll return, as:
from django.core import serializers
data = serializers.serialize('json', UserMcqAnswer.objects.raw(query), fields=('some_field_you_want', 'another_field', 'and_some_other_field'))
Good luck finding the best way to solve your issue
Edit: small fix, added an import

Answer 2

Using raw query is not recommended in Django.
When the model query APIs don’t go far enough, you can fall back to writing raw SQL.
In your case model query API can solve your problem. You can use the following view:
views.py
def get_answers(request):
test = Test.objects.get(name="Test 1")
answers = UserMcqAnswer.objects.filter(test_id=test, user=request.user).annotate(
is_correct=Case(
When(user_answer=F('mcq_question_id__mcq_right_answer'),
then=Value(True)),
default=Value(False),
output_field=BooleanField())
).values()
return JsonResponse(list(answers), safe=False)
Also you can consider Django Rest Framework for serialization of QuerySet.