Django GROUP BY 外键查询

Question

这是我的 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)

我想做的是得到问题和 group_by QuestionCategory

所以我可以这样显示我的问题：

Question_Category (1)
- 问题(1)
  - 回答 (1)
- 问题(2)
  - 回答 (2)
.....
Question_Category (2)
- 问题(3)
  - 回答 (3)
- 问题 (...)
  - 回答 (...)
...

这是我的问题的文档：https://docs.djangoproject.com/en/1.8/topics/db/aggregation/

Answer 1

您不需要 GROUP_BY，只需使用 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

在你的views.py

def questions(request):
    categories = QuestionCategory.objects.prefetch_related('question_set').all()
    return render(request, 'question.html', {
        'questions': questions
    })

在你的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 %}

prefetch_related 用于优化您的查询。

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