migrations

migrations#

What is migrations/ in Django?#

Short definition:

Migrations are Django’s way of tracking and applying database schema changes.

In simple words:

Migrations convert your Python models into database tables.

Summary:

Django migrations are Python files that track and apply database schema changes based on your models.

Where migrations/ fits in Django#

Flow:

models.py  ➜  migrations  ➜  database (db.sqlite3 / PostgreSQL)

Django never directly changes the database.

It always uses migrations.

Structure of migrations/ folder#

Inside your app:

myapp/
├── migrations/
│   ├── __init__.py
│   └── 0001_initial.py   ← appears later

Why this is a folder?#

Because Django stores multiple migration files over time.

__init__.py inside migrations#

This file:

# empty
Purpose:

  • Marks migrations as a Python package

  • Allows Django to import migration files

You never touch this file

When are migration files created?#

Migration files are created when:

  1. You write or change models

  2. You run:

python manage.py makemigrations

Example:

# myapp/models.py
from django.db import models

class Post(models.Model):
    title = models.CharField(max_length=200)
    content = models.TextField()

Run:

python manage.py makemigrations

Django creates:

migrations/
└── 0001_initial.py

What is inside a migration file?#

Example 0001_initial.py:

from django.db import migrations, models

class Migration(migrations.Migration):

    initial = True

    dependencies = []

    operations = [
        migrations.CreateModel(
            name='Post',
            fields=[
                ('id', models.BigAutoField(primary_key=True)),
                ('title', models.CharField(max_length=200)),
                ('content', models.TextField()),
            ],
        ),
    ]
This means:

  • Create table post

  • Add columns title, content

  • Add primary key id

Two-step migration process#

Step1: Create migration files

python manage.py makemigrations

Creates files in migrations/

Step2: Apply migrations to database

python manage.py migrate

➡️ Updates db.sqlite3 (or PostgreSQL)

Migration commands you must know#

Command

Purpose

makemigrations

Create migration files

migrate

Apply migrations

showmigrations

List applied/unapplied migrations

sqlmigrate app 0001

Show SQL

migrate app zero

Rollback app

Example real workflow

# change models.py
python manage.py makemigrations
python manage.py migrate

Repeat this every time you change models.

Common beginner mistakes:

  • Editing database manually

  • Forgetting to run migrate

  • Deleting migration files randomly

  • Running migrate without makemigrations

  • Using migrations as version control

Is it safe to delete migrations?

Situation

Safe?

Early development

⚠️ Sometimes

Production

❌ NEVER

Team project

❌ NEVER

Reset local DB

⚠️ Carefully
Why migrations are powerful:

  • Database versioning

  • Rollbacks

  • Team synchronization

  • Database-agnostic (SQLite → PostgreSQL → MySQL)

  • Production safe

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