Django 1.1（当前为beta）增加了对聚合的支持。您的查询可以通过以下方式完成：
from django.db.models import Max
People.objects.annotate(max_weight=Max('roles__weight')).order_by('-max_weight')
这样可以按最重的角色对人员进行排序，而不会返回重复项。
SELECT people.id, people.name, MAX(role.weight) AS max_weight
FROM people LEFT OUTER JOIN people_roles ON (people.id = people_roles.people_id)
LEFT OUTER JOIN role ON (people_roles.role_id = role.id)
GROUP BY people.id, people.name
ORDER BY max_weight DESC
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