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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