How do I handle model relationships in Django migrations?

How do I handle model relationships in Django migrations?

In Django, you can manage model relationships in migrations by using the ForeignKey, ManyToManyField, and OneToOneField fields. When you create a migration, Django automatically detects these relationships and generates the necessary database schema.

Can you give me an example of a ForeignKey relationship?

Sure! For example, if you have a Book model and an Author model, you can define a ForeignKey in the Book model like this:

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

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

This creates a relationship where each book is linked to a specific author.

What happens if I delete an author?

If you set on_delete=models.CASCADE, deleting an author will also delete all related books. If you want to keep the books, you can use on_delete=models.SET_NULL instead, which will set the author field to NULL for those books.

How do I create a migration after changing the models?

You can create a migration by running the command python manage.py makemigrations. This will generate a migration file that reflects the changes you've made to your models.