How to implement behavior when deleting a record in a table that is linked to another via on_delete?

In Django, to specify the behavior when deleting a record associated with another through a foreign key, the on_delete parameter is used in the ForeignKey field. For example:

from django.db import models

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

class Book(models.Model):
    author = models.ForeignKey(Author, on_delete=models.CASCADE)
    title = models.CharField(max_length=100)

The on_delete values can be:

• models.CASCADE — when the parent is deleted, all related records are deleted;
• models.PROTECT — prevents deletion of the parent if related records exist;
• models.SET_NULL — sets the field to NULL upon deletion of the parent (requires null=True);
• models.SET_DEFAULT — sets the default value;
• models.DO_NOTHING — does nothing, which may lead to integrity errors.

Thus, on_delete determines what happens to dependent records when the related record is deleted.