问题
this is a simple question. I'd like to know if it is the same to write:
queryset = Model.objects.filter(field=None)
than:
queryset = Model.objects.filter(field__isnull=True)
I'm using django 1.8
回答1:
They are equal:
>>> str(Person.objects.filter(age__isnull=True).query) == str(Person.objects.filter(age=None).query)
True
>>> print(Person.objects.filter(age=None).query)
SELECT "person_person"."id", "person_person"."name", "person_person"."yes", "person_person"."age" FROM "person_person" WHERE "person_person"."age" IS NULL
>>> print(Person.objects.filter(age__isnull=True).query)
SELECT "person_person"."id", "person_person"."name", "person_person"."yes", "person_person"."age" FROM "person_person" WHERE "person_person"."age" IS NULL
回答2:
Just to keep in mind that you cannot reverse the condition with your first solution:
# YOU CANNOT DO THIS
queryset = Model.objects.filter(field!=None)
However you can do this:
queryset = Model.objects.filter(field__isnull=False)
回答3:
It depends on the type of field. As mentioned in other answers, they are usually equivalent but in general, this isn't guaranteed.
For example, the Postgres JSON field uses =None to specify that the json has the value null while __isnull=True means there is no json:
https://docs.djangoproject.com/en/3.0/ref/contrib/postgres/fields/#jsonfield
来源：https://stackoverflow.com/questions/29858701/django-query-isnull-true-or-none