在Django QuerySet中，如何过滤“不存在”以多对一的关系 [英] In a Django QuerySet, how to filter for "not exists" in a many-to-one relationship

问题描述

我有两个这样的模型：

class User(models.Model)
    email = models.EmailField()

class Report(models.Model):
    user = models.ForeignKey(User)

在现实中，每个模型都有更多的字段，这对这个问题没有任何影响。

In reality each model has more fields which are of no consequence to this question.

我想过滤所有有电子邮件的用户它以'a'开始，没有报告。根据其他字段，会有更多的 .filter（）和 .exclude（）标准。

I want to filter all users who have an email which starts with 'a' and have no reports. There will be more .filter() and .exclude() criteria based on other fields.

我想这样做：

users = User.objects.filter(email__like = 'a%')

users = users.filter(<other filters>)

users = ???

我想要???过滤掉没有与之相关联的报告的用户。我该怎么做？

I would like ??? to filter out users who do not have reports associated with them. How would I do this? If this is not possible as I have presented it, what is an alternate approach?

推荐答案

使用 isnull 。

users_without_reports = User.objects.filter(report__isnull=True)
users_with_reports = User.objects.filter(report__isnull=False).distinct()

当您使用 isnull = False 需要 distinct（）以防止重复的结果。

When you use isnull=False, the distinct() is required to prevent duplicate results.

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