Django GROUP BY ForeignKey query - group-by

Question

This is my models.py:
class QuestionCategory(models.Model):
name = models.CharField(max_length=200)
class Question(models.Model):
question = models.CharField(max_length=200)
answer = models.TextField()
category = models.ForeignKey(QuestionCategory)
What I want to do is to get the questions and group_by the QuestionCategory
So I can display my questions like this:
Question_Category (1)
Question (1)
Answer (1)
Question (2)
Answer (2)
....
Question_Category (2)
Question (3)
Answer (3)
Question (...)
Answer (...)
...
This is the doc to my question: https://docs.djangoproject.com/en/1.8/topics/db/aggregation/

Answer 1

You do not need GROUP_BY, just use reverse foreignkey lookup:
categories = QuestionCategory.objects.prefetch_related('question_set').all()
for category in categories:
print category.name
for question in category.question_set.all():
print question.question
print question.answer
In your views.py
def questions(request):
categories = QuestionCategory.objects.prefetch_related('question_set').all()
return render(request, 'question.html', {
'questions': questions
})
In your question.html
{% for category in categories %}
<h2>{{ category.name }}</h2>
{% for question in category.question_set.all %}
<h3>{{ question.question }}</h3>
<p>{{ question.answer }}</p>
{% endfor %}
{% endfor %}
The prefetch_related is use to optimise your query.