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"""
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"
)
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