mirror of
https://github.com/django/django.git
synced 2024-12-25 02:26:12 +00:00
34 lines
764 B
Python
34 lines
764 B
Python
"""
|
|
Many-to-one relationships that can be null
|
|
|
|
To define a many-to-one relationship that can have a null foreign key, use
|
|
``ForeignKey()`` with ``null=True`` .
|
|
"""
|
|
|
|
from django.db import models
|
|
|
|
|
|
class Reporter(models.Model):
|
|
name = models.CharField(max_length=30)
|
|
|
|
|
|
class Article(models.Model):
|
|
headline = models.CharField(max_length=100)
|
|
reporter = models.ForeignKey(Reporter, models.SET_NULL, null=True)
|
|
|
|
class Meta:
|
|
ordering = ("headline",)
|
|
|
|
def __str__(self):
|
|
return self.headline
|
|
|
|
|
|
class Car(models.Model):
|
|
make = models.CharField(max_length=100, null=True, unique=True)
|
|
|
|
|
|
class Driver(models.Model):
|
|
car = models.ForeignKey(
|
|
Car, models.SET_NULL, to_field="make", null=True, related_name="drivers"
|
|
)
|