Django 1.6如何同时正确注释Count()和Sum()? [英] Django 1.6 how to correctly annotate Count() and Sum() at the same time?

问题描述

简单描述:

#for Question中的每个q，q.votes是正确的Question.objects.annotate(votes = Sum('vote__value'))#添加计数注释，q.answers是正确的，而q.votes不正确.Question.objects.annotate(votes = Sum('vote__value'，distinct = True)，answers = Count('answer'，distinct = True)，)

如果我想同时注释Count()和Sum()，如何?因此，我可以做类似的事情:

If I want to annotate Count() and Sum() at the same time, How? Thus I can do something like:

qs = Question.objects.annotate(votes=Sum('vote__value', distinct=True),answers=Count('answer', distinct=True),)
for q in qs:
    #do something with q.votes and q.answers in a template
    #this will be convenient.

单击此处，以根据需要下载测试项目代码.测试功能在raw.tests.test()

Click Here to download the test project code if needed.Test function is in raw.tests.test()

推荐答案

在Django 1.11中，您可以使用

With Django 1.11 you can use Subquery()

votes = Vote.objects.filter(question=OuterRef('pk').order_by().values('question')
sum_votes = votes.annotate(s=Sum('value')).values('s')

answers = Answer.objects.filter(question=OuterRef('pk').order_by().values('question')
count_answers = answers.annotate(c=Count('*')).values('c')

qs = Question.objects.annotate(votes=Subquery(sum_votes),
                               answers=Subquery(count_answers))

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