How to Use Multiple Databases in Django

August 15, 2022

Django ORM very well designed to use multiple relational databases (regardless engine) in single project. To start using two databases in Django project you need to configure connection to all of them in the settings.py file.

Configuration #

DATABASES = {
    'default': {
        'ENGINE': 'django.db.backends.sqlite3',
        'NAME': BASE_DIR / 'global_airports_sqlite.db',
    }
    'second_database': {
        'ENGINE': 'django.db.backends.sqlite3',
        'NAME': BASE_DIR / 'second_database.db',
    }
}

Once it will be configured you can query data from the database that is not ‘default’ using using('<database_connection_name>')

Post.objects.using('second_database').all()

Same for write

Post.objects.using('second_database').create(
    name='First Post',
    category_id=1,
)

It also can be more dynamic, you can assign database connection name to the variable and use it this way

database_name = 'second_database'
Post.objects.using(database_name).create(
    name='First Post',
    category_id=1,
)

Migrations #

By default Django assume that any model can by queried using any configured database, so you need to apply migrations for each database.

Widely used command python manage.py migrate apply migrations to all database, to apply migrations to the specific database you may to to specify database connection name this way

python manage.py migrate --database=second_database

If you need more flexible configuration using multiple databases such as

• Limit some model to use some database by default
• Limit all models from the some app to use some database by default
• Apply only certain migrations migrations per app/model
• Allow relation (foreignKey/one-to-one) between objects in different databases

It is all possible but you need to create your custom database router.