使用django获取对象的孙子 [英] Get grandchildren of an object with django

问题描述

我正在使用Django构建具有以下模型的Web应用程序：

I'm building a webapp with django with the following models:

class Business(models.Model):
    ...

class Branch(models.Model):
    business = models.ForeignKey(Business)
    ...

class Event(models.Model):
    branch = models.ForeignKey(Branch)

我的问题是我该如何按其业务（而不是其分支机构）获取所有事件，以及如何在数据库查询中获取所有事件。

My questions is how can I get all events by their business (not their branch), and if it possible to do so in a DB query.

谢谢！

推荐答案

Django查询集允许您使用 __表示法来访问关系。您可以深入了解它并进一步了解它此处。

Django querysets allow you to use the "__" notation to access relationships. You can take it to any depth and read more about it here.

Django提供了一种强大而直观的方式来跟踪查找中的关系
，在
背后自动为您处理SQL JOIN。要扩展关系，只需在各个模型中使用相关
字段的字段名称，并用双下划线将其分隔，直到获得所需的字段
。

Django offers a powerful and intuitive way to "follow" relationships in lookups, taking care of the SQL JOINs for you automatically, behind the scenes. To span a relationship, just use the field name of related fields across models, separated by double underscores, until you get to the field you want.

以下任何一种情况均适用：

Any of the following should work in your case:

Event.objects.filter(branch__business=<business>)
Event.objects.filter(branch__business_id=<business-id>)
Event.objects.filter(branch__business__id=<business-id>)
# if business had a name field you could also use
Event.objects.filter(branch__business__name=name-of-business)

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