Django 如果 PK 从其他表中删除，则 select_related 返回空查询集

Question

Consider I am having a table that having a foreignkey relation with the user model.假设我有一个与用户 model 具有外键关系的表。

class MyModel(models.Model):
       created_user = models.ForeignKey(settings.AUTH_USER_MODEL)

I am taking queryset like this我正在接受这样的查询集

qs = MyModel.objects.select_related('created_user').all()

This query working fine, but if the user deleted from the database, then it is showing empty queryset .此查询工作正常，但如果用户从数据库中删除，则显示为空查询集。

Answer 1

If you want the instance to be protected after deletion then you can use models.PROTECT option so:如果您希望实例在删除后受到保护，那么您可以使用models.PROTECT选项：

class MyModel(models.Model):
       created_user = models.ForeignKey(settings.AUTH_USER_MODEL, on_delete=models.PROTECT)

See all the options of ForeignKey.on_delete .查看ForeignKey.on_delete的所有选项。