**Course Title:** Mastering Django Framework: Building Scalable Web Applications **Section Title:** Models and Database Operations **Topic:** Introduction to Django models and database schema design **Overview** In this topic, we will delve into the world of Django models and database schema design. Django's ORM (Object-Relational Mapping) system allows us to interact with the database using Python code, making it easier to manage complex database operations. We will explore how to define models, create database tables, and perform CRUD (Create, Read, Update, Delete) operations. **What are Django Models?** Django models are Python classes that represent database tables. They define the structure of the data, including the fields, relationships, and constraints. Models are the foundation of Django's ORM system, allowing us to interact with the database using Python code. **Defining Models in Django** To create a model in Django, we need to define a Python class that inherits from `django.db.models.Model`. Here's an example of a simple model: ```python # models.py from django.db import models class Book(models.Model): title = models.CharField(max_length=200) author = models.CharField(max_length=100) publication_date = models.DateField() ``` In this example, we define a `Book` model with three fields: `title`, `author`, and `publication_date`. Each field is an instance of a Django field class, which defines the characteristics of the field, such as its data type and constraints. **Database Schema Design** Django's ORM system automatically creates the database schema based on the models we define. However, we can also customize the schema by using various options and settings. Here are some key concepts to keep in mind when designing a database schema: * **Primary keys**: A primary key is a unique identifier for each record in a table. In Django, the primary key is automatically created as an `id` field. * **Foreign keys**: A foreign key is a field that references the primary key of another table. This allows us to establish relationships between tables. * **Indexes**: An index is a data structure that improves query performance by allowing the database to quickly locate specific records. * **Constraints**: Constraints are rules that enforce data integrity, such as ensuring that a field contains only valid values. **Example Use Case** Let's say we want to create a database schema for a simple e-commerce application. We have two models: `Product` and `Order`. The `Product` model has fields for `name`, `price`, and `description`, while the `Order` model has fields for `product`, `quantity`, and `total`. Here's an example of how we might define these models: ```python # models.py from django.db import models class Product(models.Model): name = models.CharField(max_length=200) price = models.DecimalField(max_digits=10, decimal_places=2) description = models.TextField() class Order(models.Model): product = models.ForeignKey(Product, on_delete=models.CASCADE) quantity = models.IntegerField() total = models.DecimalField(max_digits=10, decimal_places=2) ``` In this example, we define two models: `Product` and `Order`. The `Product` model has fields for `name`, `price`, and `description`, while the `Order` model has fields for `product`, `quantity`, and `total`. We also establish a foreign key relationship between the `Order` model and the `Product` model, allowing us to link an order to a specific product. **Conclusion** In this topic, we explored the basics of Django models and database schema design. We learned how to define models, create database tables, and perform CRUD operations. We also discussed key concepts such as primary keys, foreign keys, indexes, and constraints. **What's Next?** In the next topic, we will explore how to use Django's ORM for database operations. We will learn how to perform CRUD operations, use querysets, and optimize database queries. **Leave a comment or ask for help if you have any questions or need further clarification on any of the concepts covered in this topic.** **External Resources:** * Django documentation: <https://docs.djangoproject.com/en/4.1/> * Django ORM tutorial: <https://docs.djangoproject.com/en/4.1/topics/db/models/> * Django database schema design: <https://docs.djangoproject.com/en/4.1/ref/models/fields/>