To define a **Many-to-One** relation, `models.ForeignKey` is used. The first argument corresponds to the model to relate to, and the second, '**on_delete**', specifies the behavior when the related object is deleted. The options include:
- **CASCADE**: Deleting a genre deletes all associated books.
- **PROTECT**: Prevents deletion if there are related books.
- **SET_NULL**: Sets the genre to Null if **null=True** in model definition.
- **SET_DEFAULT**: Sets a default value if the genre is deleted if there available some default value.
- **DO_NOTHING**: No action, but may lead to **IntegrityError**.

The `related_name` argument in ForeignKey is useful for **reverse relation** from the `Genre` model back to `Book` model. If you don't specify a `related_name`, Django automatically creates one using the name of your model with the suffix **_set** (Genre.book_set.all()). 

In our case works:
``` python
biography.books.all()  # provides all books of the given genre

Book.objects.filter(genre__format='history') # retrieve all books of the given genre
```


This structure provides a clear understanding of the **Many-to-One** relationship in Django, showcasing how to define and utilize it effectively.

What does 'models.ForeignKey' do in a Django model?

What happens when 'on_delete=models.CASCADE' is set in a ForeignKey relationship?

What is the purpose of the 'related_name' argument in a ForeignKey field?

Aprende a construir aplicaciones utilizando el framework Django ORM. Este es el siguiente paso en la expansión de su conocimiento del desarrollo de Django.

A quick overview of the Django ORM. One of the advantages of Django is the Django ORM.

You will learn about Django's robust modeling system, including field data types for precise database structuring. The section also covers migrations for seamless schema updates and the powerful admin interface, providing an intuitive way to manage your application's data.

This essential section is your treasure map for navigating Create, Read, Update, and Delete (CRUD) operations. Effortlessly craft queries to add new records, fetch and explore data with finesse, seamlessly update existing records, and confidently delete what's no longer needed. Each example is a key, unlocking the power and elegance of Django ORM. 🌟🔍💻🚀

Explore the intricate world of database relationships in Django! This section delves into the core concepts of Many-to-One, One-to-One, and Many-to-Many relationships. Learn how to effectively model real-world scenarios in your database using Django's powerful ORM, with clear examples and practical use-cases to guide you.

After this section, you will be able to master Django's field lookups, Q and F objects for advanced queries, and Aggregation and Annotation for data summarization. You'll also learn techniques to minimize database hits, addressing the N+1 problem, and effectively using select and prefetch related.

This section delves into advanced Django concepts, including the Meta class for model customization, the implementation of constraints for data integrity, the basics of transactions for ensuring database consistency, and an overview of the User model, a core component for handling user authentication and permissions in Django applications.

Django ORM Ninja: Técnicas Avanzadas para Desarrolladores

ForeignKey Arguments

1. What does 'models.ForeignKey' do in a Django model?

2. What happens when 'on_delete=models.CASCADE' is set in a ForeignKey relationship?

3. What is the purpose of the 'related_name' argument in a ForeignKey field?