We have three tables now:

1. authors

2. author_profiles (ONE-TO-ONE with authors)

3. books (ONE-TO-MANY with authors)

Table: authors

id	name	email	is_active	created_at
1	George Orwell	orwell@example.com	true	2026-01-21 10:15:00
2	Rowling	rowling@example.com	true	2026-01-21 10:20:00
3	Leo Tolstoy	tolstoy@example.com	false	2026-01-21 10:25:00

Note

• id is auto-generated

• email is UNIQUE

• is_active = false means inactive author

---

Table: author_profiles (ONE-TO-ONE)

id	author_id	bio	website	birth_year
1	1	English novelist and journalist	https://example.com/orwell	1903
2	2	British author, philanthropist	https://example.com/rowling	1965

Note

Important:

• author_id is UNIQUE

• Author id = 3 has NO profile (this is allowed)

• But no author can have more than one profile

---

Table: books

id	author_id	title	published_year	price	is_published
1	1	1984	1949	9.99	true
2	1	Animal Farm	1945	7.99	true
3	2	Harry Potter	1997	19.99	true
4	2	The Casual Vacancy	2012	14.50	true
5	3	War and Peace	1869	12.00	false

Note

• author_id links to authors.id

• (author_id, title) must be UNIQUE

• is_published = false means draft/unpublished

---

How Django ORM sees these rows

One-to-One access

author = Author.objects.get(id=1)
author.profile.bio

➡️ “English novelist and journalist”

Reverse One-to-One

profile = AuthorProfile.objects.get(author_id=1)
profile.author.name

➡️ “George Orwell”

One-to-Many access

author.books.all()

Returns multiple rows from books.

---

Relationship diagram

authors
+----+----------------+
| id | name           |
+----+----------------+
| 1  | George Orwell  |
+----+----------------+
        │
        │  (one-to-one)
        ▼
author_profiles
+----+-----------+--------------------+
| id | author_id | bio                |
+----+-----------+--------------------+
| 1  | 1         | English novelist   |
+----+-----------+--------------------+

        │
        │  (one-to-many)
        ▼
books
+----+-----------+-------------+
| id | author_id | title       |
+----+-----------+-------------+
| 1  | 1         | 1984        |
| 2  | 1         | Animal Farm |
+----+-----------+-------------+

---

models.py

Add a new model without changing existing ones.

from django.db import models
from django.core.validators import MinValueValidator

class Author(models.Model):
    name = models.CharField(max_length=200)
    email = models.EmailField(unique=True)
    is_active = models.BooleanField(default=True)
    created_at = models.DateTimeField(auto_now_add=True)

    class Meta:
        db_table = "authors"

    def __str__(self):
        return self.name

class AuthorProfile(models.Model):
    author = models.OneToOneField(
        Author,
        on_delete=models.CASCADE,
        related_name="profile",
    )
    bio = models.TextField(blank=True)
    website = models.URLField(blank=True)
    birth_year = models.PositiveSmallIntegerField(null=True, blank=True)

    class Meta:
        db_table = "author_profiles"

    def __str__(self):
        return f"Profile of {self.author.name}"

class Book(models.Model):
    author = models.ForeignKey(
        Author,
        on_delete=models.CASCADE,
        related_name="books",
    )
    title = models.CharField(max_length=200)
    published_year = models.PositiveSmallIntegerField(
        validators=[MinValueValidator(1)]
    )
    price = models.DecimalField(max_digits=8, decimal_places=2)
    is_published = models.BooleanField(default=True)

    class Meta:
        db_table = "books"
        constraints = [
            models.UniqueConstraint(
                fields=["author", "title"],
                name="uniq_book_per_author",
            )
        ]

    def __str__(self):
        return self.title

Run migrations

python manage.py makemigrations myapp
python manage.py migrate