How to create a Django model with a ForeignKey relationship



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In Django, you can create a model with a ForeignKey relationship by using the ForeignKey field. The ForeignKey field is used to create a many-to-one relationship between two models. Here's an example of how to create a Django model with a ForeignKey relationship:

Let's say you have two models: Author and Book. Each book is written by an author, and you want to establish a ForeignKey relationship between them.

python
# models.py

from django.db import models

class Author(models.Model):
    name = models.CharField(max_length=100)
    bio = models.TextField()

    def __str__(self):
        return self.name

class Book(models.Model):
    title = models.CharField(max_length=200)
    published_date = models.DateField()
    author = models.ForeignKey(Author, on_delete=models.CASCADE)

    def __str__(self):
        return self.title

In the example above:

  • The Author model has two fields: name and bio.
  • The Book model has three fields: title, published_date, and author.
  • The author field in the Book model is a ForeignKey field that establishes a many-to-one relationship with the Author model. The on_delete=models.CASCADE argument means that if an Author is deleted, all associated Book objects will also be deleted.

After defining your models, you'll need to run the following commands to apply these changes to your database:

bash
python manage.py makemigrations
python manage.py migrate

These commands will create the necessary database tables based on your model definitions.

Now you can use these models in your Django application. For example, you can create an author and associate books with that author:

python
# Creating an author
author = Author.objects.create(name='John Doe', bio='A prolific author.')

# Creating books associated with the author
book1 = Book.objects.create(title='Book 1', published_date='2023-01-01', author=author)
book2 = Book.objects.create(title='Book 2', published_date='2023-02-01', author=author)

This establishes a relationship between the Author and Book models, where each book is associated with a specific author through the author field.

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