.. _tutorial-dbinit: Step 4: Creating The Database ============================= As outlined earlier, Flaskr is a database powered application, and more precisely, it is an application powered by a relational database system. Such systems need a schema that tells them how to store that information. So before starting the server for the first time it's important to create that schema. Such a schema can be created by piping the `schema.sql` file into the `sqlite3` command as follows:: sqlite3 /tmp/flaskr.db < schema.sql The downside of this is that it requires the sqlite3 command to be installed which is not necessarily the case on every system. This also requires that we provide the path to the database which can introduce errors. It's a good idea to add a function that initializes the database for you to the application. To do this we can create a function and hook it into the ``flask`` command that initializes the database. Let me show you the code first. Just add this function below the `connect_db` function in `flaskr.py`:: def init_db(): db = get_db() with app.open_resource('schema.sql', mode='r') as f: db.cursor().executescript(f.read()) db.commit() @app.cli.command('initdb') def initdb_command(): """Initializes the database.""" init_db() print 'Initialized the database.' The ``app.cli.command()`` decorator registers a new command with the ``flask`` script. When the command executes Flask will automatically create a application context for us bound to the right application. Within the function we can then access :attr:`flask.g` and other things as we would expect. When the script ends, the application context tears down and the database connection is released. We want to keep an actual functions around that initializes the database though so that we can easily create databases in unittests later. (For more information see :ref:`testing`.) The :func:`~flask.Flask.open_resource` method of the application object is a convenient helper function that will open a resource that the application provides. This function opens a file from the resource location (your `flaskr` folder) and allows you to read from it. We are using this here to execute a script on the database connection. The connection object provided by SQLite can give us a cursor object. On that cursor there is a method to execute a complete script. Finally we only have to commit the changes. SQLite 3 and other transactional databases will not commit unless you explicitly tell it to. Now it is possible to create a database with the ``flask`` script:: flask --app=flaskr initdb Initialized the database. .. admonition:: Troubleshooting If you get an exception later that a table cannot be found check that you did execute the `initdb` command and that your table names are correct (singular vs. plural for example). Continue with :ref:`tutorial-views`