******************
Database Migration
******************

    "Migrations are Django’s way of propagating changes you make to your models
    (adding a field, deleting a model, etc.) into your database schema."

    -- :djangodocs:`Migrations | Django documentation <topics/migrations/>`

Now that you have created the models, the next step is to create the tables in
the database.

.. index:: makemigrations, migrate, Database migration

Create the migration
====================

The first step is to create a migration so that Django’s migration framework
knows about the new models you created. You do that by running the
:command:`makemigrations` command:

::

    $ python manage.py makemigrations marcador
    Migrations for 'marcador':
      0001_initial.py:
        - Create model Bookmark
        - Create model Tag
        - Add field tags to bookmark

This will create the new file :file:`0001_initial.py` in the directory
:file:`migrations` of the app :file:`marcador`:

::

    marcador
    |-- __init__.py
    |-- admin.py
    |-- migrations
    |   |-- 0001_initial.py
    |   `-- __init__.py
    |-- models.py
    |-- tests.py
    `-- views.py

.. raw:: latex

    \newpage

Migrate the database
====================

After that you have to apply the migration you just created as well as the
already existing migrations to create the database schema by using the
:command:`migrate` command:

::

    $ python manage.py migrate
    Operations to perform:
      Synchronize unmigrated apps: staticfiles, messages
      Apply all migrations: admin, contenttypes, marcador, auth, sessions
    Synchronizing apps without migrations:
      Creating tables...
        Running deferred SQL...
      Installing custom SQL...
    Running migrations:
      Rendering model states... DONE
      Applying contenttypes.0001_initial... OK
      Applying auth.0001_initial... OK
      Applying admin.0001_initial... OK
      Applying contenttypes.0002_remove_content_type_name... OK
      Applying auth.0002_alter_permission_name_max_length... OK
      Applying auth.0003_alter_user_email_max_length... OK
      Applying auth.0004_alter_user_username_opts... OK
      Applying auth.0005_alter_user_last_login_null... OK
      Applying auth.0006_require_contenttypes_0002... OK
      Applying marcador.0001_initial... OK
      Applying sessions.0001_initial... OK

Now all tables defined in the migrations have been created in the database.