如何在django中查询SELECT WHERE EXISTS ... [英] How to query SELECT WHERE EXISTS... in django

问题描述

我有一个django模型的问题，我不知道如何创建一个查询...

I have a problem with django models, I don't know how to create a query...

我有三个类/模型：

• A只有名称（和id）


• B具有A的名称，ID和外键


• C在其他字段中有B的外键。

所以每个C都有它的A A可以有更多的As）但是没有直接的外键 - 它必须经过B。

So every C has its A (while every A can have more As) but doesn't have its foreign key directly - it has to go through B.

我有一个Cs的子集被另一个查询。现在我想选择这样的As，在子集中有一个C。我该怎么办？

I have a subset of Cs got by another query. Now I want to select such As for which there is a C in the subset. What do I do?

推荐答案

假设 c_subset 是 C 您拥有的对象，以获得 A ，其中包含这些 C s
你可以做

Assuming c_subset is subset of C objects that you have, to get As which has these Cs you can do

>>> A.objects.filter(b__c__in = c_subset)

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