Note that you must save an object before it can be assigned to a foreign key relationship. For example, creating anArticlewith unsavedReporterraisesValueError: >>>r3=Reporter(first_name='John',last_name='Smith',email='john@example.com')>>>Article.objects.create(headline="This is a test",p...
LZ,Django官方所说的one-to-many只是它的写法而已,不具有指向性。更明确的是外键这种叫法。 如果按照你所理解的具有指向性,那么就要写成one-to-many和many-to-one了。 但要注意:one-to-one和foreignkey(unique=True)两种确实有指向性,至少在调用的时候会有这种差别。有用 回复 撰写回答 你尚未登录,登录后可以...
If you want the reverse relationship, you would need to add two ForeignKey fields to your PhoneNumber model, one to Dude and one to Business. This would allow each number to belong to either one Dude or one Business, and have Dudes and Businesses able to own multiple Numbers. I think th...
To define a many-to-one relationship, use ForeignKey.In this example, a Reporter can be associated with many Article objects, but an Article can only have one Reporter object:from django.db import models class Reporter(models.Model): first_name = models.CharField(max_length=30) last_name =...
When summing through a One-to-Many relationship on the property of a JSONField, there is the following error TypeError: the JSON object must be str, bytes or bytearray, not int To reproduce the error, you can create a model that is linked to another model with a JSONField: ...
field pointed at the model on the "one" side of the relationship, a OneToOneField field pointed at the model on the "many" side (to ensure the unique relationship to the "one" side), and another field storing the sort value (to remember to orders of the objects on the "many" side)...
Many-to-many relationship to Permission 与Permission属于多对多的关系,而Permission表示的是权限,由另一种表储存。 关于权限的问题需要另外说明,这里暂时不讨论。 is_active 表用户是否是活跃的,是一个布尔值。django提议与其删除一个用户的所有信息,还不如将其设置为非活跃(即冻结)状态。这样不会破坏其他相关的外...
书籍有两四个属性:书名、出版日期、作者、出版社。有一个或多个作者(和作者是多对多的关联关系[many-to-many]), 只有一个出版商(和出版商是一对多的关联关系[one-to-many],也被称作外键[foreign key]) 所以我们编写代码如下: fromdjango.dbimportmodelsclassAuthor(models.Model):name=models.CharField(max_len...
书籍有两四个属性:书名、出版日期、作者、出版社。有一个或多个作者(和作者是多对多的关联关系[many-to-many]), 只有一个出版商(和出版商是一对多的关联关系[one-to-many],也被称作外键[foreign key]) 所以我们编写代码如下: 所以我们在为属性命名的时候,要避免使用数据库的关键字。另外,我们只需要关心每个...
说是ForeignKey是one-to-many的，并举了一个车的例子：有两个配件表，一个是车轮表，另一个是引擎表。两个表都有一个car字段，表示该配件对应的车。对于车轮来说，多个对应一个car的情况很正常，所以car字段应该用ForeignKey来表示。对于引擎来说，一个引擎只可能对应一个car，所以必须用OneToOneField。