Django Models - Introduction

1. Introduction

In Django, models are the backbone of your application’s data layer. They define the structure of your data, how it’s stored, and how it behaves. Instead of writing raw SQL to create and manage tables, you define Python classes that represent your database tables — and Django takes care of the rest.

2. What is a Django Model?

A model is the single, definitive source of information about your data. It contains the essential fields and behaviors of the data you’re storing.

• Each model is a Python class that subclasses django.db.models.Model.
• Each class attribute represents a database field.
• Django automatically provides a database access API for making queries.

This means you can work with Python objects instead of manually writing SQL.

3. Why Use Django Models?

• Abstract away SQL into Pythonic syntax.
• Automatically create and update tables with migrations.
• Provide a clean API for queries, updates, and relationships.
• Enforce consistency between your code and your database schema.

4. How to Use Django Models

Quick Example

Here’s a simple model for storing product details:

from django.db import models

class Product(models.Model):
    name = models.CharField(max_length=100)
    price = models.DecimalField(max_digits=8, decimal_places=2)

• name and price are fields of the model.
• Each field maps to a database column.

This model would create a database table like:

CREATE TABLE shop_product (
    "id" bigint NOT NULL PRIMARY KEY GENERATED BY DEFAULT AS IDENTITY,
    "name" varchar(100) NOT NULL,
    "price" numeric(8, 2) NOT NULL
);

Technical Notes

• The table name (shop_product) is auto-generated but can be overridden.
• Django automatically adds an id field as the primary key (can also be overridden).
• SQL is tailored to your chosen database backend (PostgreSQL, MySQL, SQLite, etc.).

5. Using Models in Your Project

After defining models, you need to register your app with Django:

Edit your settings.py → add your app to INSTALLED_APPS:

INSTALLED_APPS = [
    # ...
    "shop",  # the app containing models.py
    # ...
]

Finally, apply migrations to create/update database tables:

python manage.py makemigrations
python manage.py migrate

6. Use Cases & Examples

• Contacts App → Contact(name, email, phone)
• Blog App → Post(title, content, published_date)
• E-commerce App → Product(name, price, stock)

7. Frequently Asked Questions (Community-Driven)

• Q1: Can I customize the table name? A: Yes. Use class Meta: db_table = "custom_name" inside your model.
• Q2: What if I don’t want an id field? A: You can override Django’s default primary key with your own field.
• Q3: Do I always need migrations? A: Yes. After modifying models, always run makemigrations and migrate.

8. Best Practices & Tips

• Always define max_length for CharField.
• Use descriptive model names (e.g., Product not Prod).
• Group related models into one app.
• Keep models.py clean — move query logic into Managers if complex.

9. Common Errors & Debugging

• Error: no such table: shop_product → Forgot to run migrate.
• Error: Field name typo → Check spelling in both model and queries.
• Error: Migration conflicts → Run makemigrations --merge.

10. Further Reading & References

• Official Django Models Docs (5.2)
• Making Queries
• Related guides: Django Migrations, QuerySets, Managers.

11. Conclusion

Django models provide a powerful and flexible way to design your database schema. By understanding how to define and use models effectively, you'll be able to build robust and scalable applications with ease.

Remember to always keep your models in sync with your application's evolving needs by running migrations as necessary. With practice and experience, you'll become proficient in using Django models to create complex and dynamic databases that support your projects' growth.

✅ Next up: Learn how to Automatically Register All Models In Django Admin.