Base on the Flask Mega-Tutorial: https://blog.miguelgrinberg.com/post/the-flask-mega -tutorial-part-iv-database

Multiple versions of the database are stored in the folder. When a change occurs on any of the database models (see backend/models.py), you must execute this command in order to create the migration script:

flask db migrate -m "version description"

Next, to apply changes, execute this command:

flask db upgrade

There also exists the flask db downgrade to revert last migration if needed.

*Note: the FLASK_APP environment variable must be defined in order for it to work.