Introduction to ORM in Django

July 07, 2025

When building web applications, working with databases is essential — but writing raw SQL for every operation can be tedious and error-prone. Django’s Object-Relational Mapping (ORM) offers a powerful way to interact with databases using Python code instead of SQL, simplifying development and improving productivity.

What is an ORM?

An Object-Relational Mapper (ORM) is a tool that maps database tables to programming language objects. In Django, each table corresponds to a Python class (a model), and each column is represented by a class attribute. This abstraction lets you work with familiar Python syntax while Django handles SQL queries behind the scenes.

Why use Django ORM?

✅ Ease of use — Perform complex database operations using simple Python methods.

✅ Database-agnostic — Switch between databases (like PostgreSQL, MySQL, SQLite) with minimal changes.

✅ Security — Protects against SQL injection by safely constructing queries.

✅ Productivity — Reduces boilerplate code and speeds up development.

Defining models

In Django, you define models in your app’s models.py file. Here’s an example of a simple Book model:

from django.db import models

class Book(models.Model):

title = models.CharField(max_length=200)

author = models.CharField(max_length=100)

published_date = models.DateField()

price = models.DecimalField(max_digits=6, decimal_places=2)

def __str__(self):

return f"{self.title} by {self.author}"

Once defined, run python manage.py makemigrations and python manage.py migrate to create the corresponding database table.

Basic CRUD with Django ORM

✅ Create

book = Book.objects.create(title="Django Basics", author="Jane Doe", published_date="2023-01-01", price=29.99)

✅ Read

all_books = Book.objects.all()

book = Book.objects.get(id=1)

✅ Update

book.title = "Advanced Django"

book.save()

✅ Delete

book.delete()

Querying with filters

The ORM supports powerful queries with filter(), exclude(), and chaining:

recent_books = Book.objects.filter(published_date__year=2023)

affordable_books = Book.objects.filter(price__lt=50)

Conclusion

Django’s ORM is one of its greatest strengths, allowing you to manage data intuitively and securely with Python objects. By mastering the ORM, you can build robust, database-driven web applications faster and with fewer bugs.

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