Django ORM按一列分组并返回另一列 [英] Django ORM group by one column and return other

问题描述

在简单的世界中，我尝试在Django中编写一个查询，该查询将返回结果

In simple worlds I try to write in Django a query which will return results

与此类似:

select id, max(score), screen, details from results
group by screen
where user_id=123
order by score desc, screen

我的代码:

results = Results.objects.filter(user=user).values('screen').annotate(score=Max('score')).order_by('-score', 'screen')

但是我没有返回结果对象，而是json.我想获得结果作为

But i doesn't return Results objects but json. I would like to get results as Results object like

user = User.objects.filter(id=id)
results = Results.objects.filter(user=user).order_by('-score', 'screen')

任何人都可以帮忙吗?

推荐答案

它是如果要将其保留为QuerySet，但仅从感兴趣的数据库中检索字段，请使用

If you want to keep it a QuerySet, but only retrieve the fields from the database that you are interested in, use only(*fields) or defer(*fields)

results = Results.objects.filter(user=user)
                         .annotate(score=Max('score'))
                         .order_by('-score', 'screen')
                         .only('screen')  # not values()

如果尝试访问实例上延迟的字段，将导致额外的数据库命中.您可以验证以下是否是不完整的Results实例:

If you try to access fields that were deferred on instances it will result in extra db hits. You can verify that these are incomplete Results instances:

> type(results[0])
<class 'app_name.Results_Deferred_foo_bar_7265632c0017c141e84a00d9fdb4760'>

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