Question

I have a model like this:

from django.db import models

class House(models.Model):
    address = models.CharField(max_length=200)
    price = models.CharField(max_length=200)

class Inhabitant(models.Model):
    home = models.ForeignKey(House, blank=True, null=True, on_delete=models.SET_NULL)
    name = models.CharField(max_length=200)
    age = models.IntegerField()

However when running python manage.py sql my_test_app I get this at the end:

ALTER TABLE `my_test_app_inhabitant`
ADD CONSTRAINT `house_id_refs_id_7cd928c7`
FOREIGN KEY (`home_id`)
REFERENCES `my_test_app_house` (`id`);

This means I can’t add an inhabitant without a house – how can I get around this?

Answer 1

The foreign key don’t means that you can not add an inhabitant without a house.

The constraint says: ‘if Inhabitant.house contains a value then this value must appear in House model’.

To verify that database allow inhabitants withou house you should check that house field inhabitant table allow NULL values.