Using Django ORM to Interact with Databases

 Using Django ORM to Interact with Databases

Django ORM (Object-Relational Mapping) is a powerful feature of the Django web framework that lets you interact with your database using Python code instead of writing raw SQL queries. It provides an easy, readable, and efficient way to create, retrieve, update, and delete records.


What is Django ORM?

ORM stands for Object-Relational Mapping.


It translates Python classes (called models) into database tables.


You work with Python objects instead of writing SQL.


Supports multiple databases like SQLite, PostgreSQL, MySQL, and Oracle.


Key Concepts

1. Models

Models are Python classes that define the structure of your database tables.


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from django.db import models


class Book(models.Model):

    title = models.CharField(max_length=100)

    author = models.CharField(max_length=50)

    published_date = models.DateField()

    pages = models.IntegerField()


    def __str__(self):

        return self.title

Each attribute corresponds to a database column.


Django automatically creates the table and columns based on your model.


2. Migrations

After defining or changing models, run:


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python manage.py makemigrations

python manage.py migrate

This creates or updates database tables to match your models.


Basic Database Operations with Django ORM

Creating Records

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book = Book(title="Django for Beginners", author="John Doe", published_date="2023-01-01", pages=250)

book.save()  # Saves the record in the database

Or more simply:


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Book.objects.create(title="Django ORM Guide", author="Jane Smith", published_date="2022-06-15", pages=300)

Retrieving Records

Get all books:


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books = Book.objects.all()

Filter books by author:


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django_books = Book.objects.filter(author="John Doe")

Get a single record by primary key:


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

Updating Records

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

book.pages = 275

book.save()

Or update multiple records:


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Book.objects.filter(author="John Doe").update(pages=300)

Deleting Records

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

book.delete()

Or delete multiple records:


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Book.objects.filter(author="Jane Smith").delete()

Advanced Querying

Ordering:


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books = Book.objects.order_by('published_date')

Chaining filters:


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books = Book.objects.filter(author="John Doe").exclude(pages__lt=100)

Aggregation:


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from django.db.models import Avg


average_pages = Book.objects.aggregate(Avg('pages'))

Why Use Django ORM?

Simplicity: Write database queries using Python, not SQL.


Database Abstraction: Easily switch databases without changing your code.


Security: Protects against SQL injection automatically.


Productivity: Handles complex queries with readable code.

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How to Connect Python with SQL Databases

Setting Up PostgreSQL for Full Stack Python Projects

SQL vs NoSQL: What’s Best for Full Stack Python Development?

Introduction to Databases for Full Stack Python Development

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