擅长:python、mysql、java
<p>刚刚发现Django 1.8有新的<a href="https://docs.djangoproject.com/en/1.10/ref/models/conditional-expressions/">conditional expressions feature</a>,所以现在我们可以这样做:</p>
<pre><code>events = Event.objects.all().annotate(paid_participants=models.Sum(
models.Case(
models.When(participant__is_paid=True, then=1),
default=0, output_field=models.IntegerField()
)))
</code></pre>