Django:通过'field__isnull = True'或'field = None'过滤查询集? [英] Django: filtering queryset by 'field__isnull=True' or 'field=None'?
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问题描述
我必须用一个动态值(可以是None)来过滤查询集:我可以简单地写:
I have to filter a queryset by a dynamic value (which can be None): may I simply write:
filtered_queryset = queryset.filter(field=value)
还是我应该检查None:
or shall I check for None:
if value is None:
filtered_queryset = queryset.filter(field__isnull=True)
else:
filtered_queryset = queryset.filter(field=value)
该行为是否取决于特定的DBMS?
Does the behaviour depend on the particular DBMS?
推荐答案
ORM将为您处理 None
(将其投射为NULL)并返回 QuerySet
对象,因此除非您需要捕获 None
输入,否则第一个示例很好。
The ORM will handle None
(cast it to NULL) for you and return a QuerySet
object, so unless you need to catch None
input the first example is fine.
>>> User.objects.filter(username=None)
[]
>>> type(_)
<class 'django.db.models.query.QuerySet'>
>>> str(User.objects.filter(username=None).query)
SELECT "auth_user"."id", "auth_user"."username", "auth_user"."first_name", "auth_user"."last_name", "auth_user"."email", "auth_user"."password", "auth_user"."is_staff", "auth_user"."is_active", "auth_user"."is_superuser", "auth_user"."last_login", "auth_user"."date_joined" FROM "auth_user" WHERE "auth_user"."username" IS NULL
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