Django - 间接连接查询
如何返回一个间接连接查询，该查询为我提供问题模型中的所有问题。需要注意的是，对于每个问题，我都需要能够访问 UserData 模型。间接关系是 Question -> User 和 User <- UserData （如果可能的话，我不希望更改模型结构）。
class Question(models.Model):
description = models.CharField(max_length=200)
pub_date = models.DateTimeField('date published')
image_url = models.CharField(max_length=200)
user = models.ForeignKey(User)
class Answer(models.Model):
question = models.ForeignKey(Question)
text = models.CharField(max_length=16000)
user = models.ForeignKey(User)
class UserData(models.Model):
user = models.OneToOneField(User)
access_token = models.CharField(max_length=32)
profile_image_url = models.CharField(max_length=200)
编辑：我认为这种关系被认为是“反向关系”。
How can I return an indirect joined query that gives me all of the Questions in the Question model. The caveat, is that for each question, I need to be able to access the UserData model. The indirect relationship is Question -> User and User <- UserData (I prefer not to change the model structure if possible).
class Question(models.Model):
description = models.CharField(max_length=200)
pub_date = models.DateTimeField('date published')
image_url = models.CharField(max_length=200)
user = models.ForeignKey(User)
class Answer(models.Model):
question = models.ForeignKey(Question)
text = models.CharField(max_length=16000)
user = models.ForeignKey(User)
class UserData(models.Model):
user = models.OneToOneField(User)
access_token = models.CharField(max_length=32)
profile_image_url = models.CharField(max_length=200)
Edit: I think this relationship is considered a "reverse relationship".
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将为每个问题获取
User对象和UserData对象。不支持反向关系除非在OneToOne关系中，就像您所拥有的 (如此处所示）will get both the
Userobject and theUserDataobject for every question. Reverse relationships aren't supported except inOneToOnerelationships like you have (As seen here)考虑select_lated()。
从 3 个查询，到仅使用 select_lated() 的 2 个查询，再到使用 select_lated() 给出更好参数的 1 个查询。
有趣的是，您不必调用与
('user', 'user__userdata')相关的 select：您可以看到最后一个查询仅使用 '从 3 个表中获取数据>user__userdata'：Consider select_related().
From 3 queries, to 2 queries with just select_related(), to 1 query with select_related() given better arguments.
It is interresting to note that you don't have to call selected related with
('user', 'user__userdata'): You can see the last query fetches data from the 3 tables with just 'user__userdata':