While SqlAlchemy (and Flask-SqlAlchemy) provides an easy way to create DB schema from scratch,  migration of an existing schema is bit more challenging. As soon as you change attributes  in your declarative ORM models, the underlying DB schema is to be changed for application to work.   If you need to keep data , you’ll need to modify DB schema with some DDL commands (ALTER TABLE …)  and this functionality is not part of SqlAlchemy nor Flask-SqlAlchemy. Continue reading Easy SQL Schema Migration for SqlAlchemy and Flask →