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"""
Relating an object to itself, many-to-one
To define a many-to-one relationship between a model and itself, use
``ForeignKey('self', ...)``.
In this example, a ``Category`` is related to itself. That is, each
``Category`` has a parent ``Category``.
Set ``related_name`` to designate what the reverse relationship is called.
"""
from django.db import models
class Category(models.Model):
name = models.CharField(max_length=20)
parent = models.ForeignKey('self', models.SET_NULL, blank=True, null=True, related_name='child_set')
def __str__(self):
return self.name
class Person(models.Model):
full_name = models.CharField(max_length=20)
mother = models.ForeignKey('self', models.SET_NULL, null=True, related_name='mothers_child_set')
father = models.ForeignKey('self', models.SET_NULL, null=True, related_name='fathers_child_set')
def __str__(self):
return self.full_name
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