Django Models – Designing Your Database - Learn PYTHON-BACKEND | Revochamp

Name: Django Models – Designing Your Database
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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. In Django, models are Python classes that subclass django.db.models.Model. Django uses these classes to automatically create the database tables for you via the ORM (Object-Relational Mapper).

Defining Fields

Each attribute of the model represents a database field. Django provides a wide variety of field types that handle validation and SQL mapping automatically.

PythonRead-only

from django.db import models

class Project(models.Model):
    title = models.CharField(max_length=200)
    description = models.TextField()
    created_at = models.DateTimeField(auto_now_add=True)
    is_active = models.BooleanField(default=True)
    stars = models.IntegerField(default=0)

    def __str__(self):
        return self.title

from django.db import models

class Project(models.Model):
    title = models.CharField(max_length=200)
    description = models.TextField()
    created_at = models.DateTimeField(auto_now_add=True)
    is_active = models.BooleanField(default=True)
    stars = models.IntegerField(default=0)

    def __str__(self):
        return self.title

Database Relationships

Django handles the three most common types of database relationships with ease: One-to-Many, Many-to-Many, and One-to-One.

ForeignKey: Defines a many-to-one relationship (e.g., many Tasks belong to one Project).
ManyToManyField: Defines a many-to-many relationship (e.g., a Project can have many Tags, and a Tag can be on many Projects).
OneToOneField: Defines a one-to-one relationship (e.g., a User has exactly one Profile).

Migrations: Evolving Your Schema

Migrations are Django’s way of propagating changes you make to your models (adding a field, deleting a model, etc.) into your database schema. It’s a two-step process:

BASHRead-only

# 1. Scan models and create a set of instructions
python manage.py makemigrations

# 2. Execute the instructions on the database
python manage.py migrate

# 1. Scan models and create a set of instructions
python manage.py makemigrations

# 2. Execute the instructions on the database
python manage.py migrate

Common Model Fields

Field Type	Usage	SQL Equivalent
CharField	Short to medium strings	VARCHAR
TextField	Large amounts of text	TEXT / LONGTEXT
EmailField	Strings with email validation	VARCHAR
DateTimeField	Date and time objects	DATETIME
DecimalField	Fixed-precision decimals (Money)	DECIMAL
SlugField	URL-friendly strings (hyphenated)	VARCHAR

Test Your Knowledge

of 3

Which command is used to sync your database with your model changes?

python manage.py runserver

python manage.py sync

python manage.py migrate

python manage.py update

of 3

Which field type would you use for a blog post content?

CharField

TextField

StringField

ContentField

of 3

What is the purpose of the __str__ method in a Model?

To convert the model to JSON

To provide a human-readable name for the object in the Admin panel

To save the object to the database

To encrypt sensitive strings

Frequently Asked Questions

What is the ORM?

The ORM (Object-Relational Mapper) allows you to interact with your database using Python code instead of writing raw SQL. For example, 'Project.objects.all()' replaces 'SELECT * FROM project;'.

What does 'on_delete=models.CASCADE' do?

It defines the behavior when a referenced object is deleted. CASCADE means if the 'Parent' is deleted, all 'Child' records referencing it will also be deleted.

Can I use an existing database with Django?

Yes. Django has an 'inspectdb' utility that can scan an existing database and automatically generate the Model classes for you.

from django.db import models class Project(models.Model): title = models.CharField(max_length=200) description = models.TextField() created_at = models.DateTimeField(auto_now_add=True) is_active = models.BooleanField(default=True) stars = models.IntegerField(default=0) def __str__(self): return self.title

Field Type

Usage

SQL Equivalent

CharField

Short to medium strings

VARCHAR

TextField

Large amounts of text

TEXT / LONGTEXT

EmailField

Strings with email validation

VARCHAR

DateTimeField

Date and time objects

DATETIME

DecimalField

Fixed-precision decimals (Money)

DECIMAL

SlugField

URL-friendly strings (hyphenated)

VARCHAR

Test Your Knowledge

of 3

Which command is used to sync your database with your model changes?

python manage.py runserver

python manage.py sync

python manage.py migrate

python manage.py update

of 3

Which field type would you use for a blog post content?

CharField

TextField

StringField

ContentField

of 3

What is the purpose of the __str__ method in a Model?

To convert the model to JSON

To provide a human-readable name for the object in the Admin panel

To save the object to the database

To encrypt sensitive strings

Frequently Asked Questions

What is the ORM?

The ORM (Object-Relational Mapper) allows you to interact with your database using Python code instead of writing raw SQL. For example, 'Project.objects.all()' replaces 'SELECT * FROM project;'.

What does 'on_delete=models.CASCADE' do?

It defines the behavior when a referenced object is deleted. CASCADE means if the 'Parent' is deleted, all 'Child' records referencing it will also be deleted.

Can I use an existing database with Django?

Yes. Django has an 'inspectdb' utility that can scan an existing database and automatically generate the Model classes for you.

Django Models – Designing Your Database

Django Models – Designing Your Database

What is a Django Model?

Defining Fields

Database Relationships

Migrations: Evolving Your Schema

Common Model Fields

Test Your Knowledge

Frequently Asked Questions

Need help?

Django Models – Designing Your Database

Django Models – Designing Your Database

What is a Django Model?

Defining Fields

Database Relationships

Migrations: Evolving Your Schema

Common Model Fields

Test Your Knowledge

Frequently Asked Questions

Need help?