python / intermediate
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
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from django.db import modelsclass Author(models.Model):name = models.CharField(max_length=100)email = models.EmailField()def __str__(self):return self.nameclass 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
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class Author(models.Model):
Defines the Author model inheriting from Django's Model base class
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author = models.ForeignKey(Author, on_delete=models.CASCADE)
Creates a many-to-one relationship; each Book belongs to one Author
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collaborators = models.ManyToManyField(Author)
Enables many-to-many relationship between Book and Author for collaboration
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on_delete=models.CASCADE
When the referenced Author is deleted, all related Books are automatically deleted