Django Model Relationships with ForeignKey and ManyToMany

Snippet

Django Model Relationships with ForeignKey and ManyToMany

Django's ORM handles relational data through model fields. ForeignKey creates a many-to-one relationship (one Author has many Books), while ManyToManyField allows bidirectional many-to-many relationships (Authors can collaborate on multiple Books, and Books can have multiple collaborators). The on_delete=models.CASCADE ensures referential integrity by deleting related books when an author is deleted.

snippet.py
python
from django.db import models
 
class Author(models.Model):
    name = models.CharField(max_length=100)
    email = models.EmailField()
 
    def __str__(self):
        return self.name
 
class Book(models.Model):
    title = models.CharField(max_length=200)
    author = models.ForeignKey(Author, on_delete=models.CASCADE, related_name='books')
    collaborators = models.ManyToManyField(Author, related_name='collaborated_books', blank=True)
    published_date = models.DateField()
    rating = models.DecimalField(max_digits=3, decimal_places=2, default=0.0)
 
    def __str__(self):
        return self.title

django

Breakdown

class Author(models.Model):

Defines the Author model inheriting from Django's Model base class

author = models.ForeignKey(Author, on_delete=models.CASCADE)

Creates a many-to-one relationship; each Book belongs to one Author

collaborators = models.ManyToManyField(Author)

Enables many-to-many relationship between Book and Author for collaboration

on_delete=models.CASCADE

When the referenced Author is deleted, all related Books are automatically deleted

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Django Model Relationships with ForeignKey and ManyToMany

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