Django Migrations

Introduction

In the last episode, we talked about Django Architecture and settings.py file. In this episode, we'll discuss Django Migrations.

Django Migrations

Migrations are used to update the changes (to add a new field, change the name of a field, etc.) we made in the model to the database.

Django creates migration files (a Python file) inside the migration folder for each model to create the table schema, and then each table is mapped to the respective migration files. Django also keeps track of the status of migration files whether they are successfully migrated to the database.

To perform migration-related tasks, we can use these commands.

makemigrations

python manage.py makemigrations

This is used to create migrations files in the migrations folder based on the changes we have done to the Model.

migrate

python manage.py migrate

Based on the migrations file, this command will populate the database schema.

showmigrations

python manage.py showmigrations

This lists all the migrations and their status. If the change is updated in the database, the status will be shown as [X] followed by the migration name.
For example:

[X] 0001_initial
[  ] 0002_auto_20210924_1740

sqlmigrate

Usage:

python manage.py sqlmigrate <app_name> <migration_name>

This is used to display the raw SQL query of the applied migrations. For example:

python manage.py sqlmigrate users 0009_delete_profile

will give the raw SQL query like as below

BEGIN;
DROP TABLE "users_profile" CASCADE;
COMMIT;

Miscellaneous Commands and Uses

• syncdb

python manage.py migrate --run-syncdb

This command allows us for creating tables for apps without migrations.

• Creating and applying migration for a particular app

If we don't want to apply migrations totally, we can mention app-name to migrate specific apps.

For example:

python manage.py makemigrations blog

python manage.py migrate blog

References

• Django Javatpoint

• Django Official Documentation

• Real Python