如何在不丢失新数据的情况下回滚数据库部署？

My company uses virtual machines for our web/app servers. This allows for very easy rollbacks of a deployment if something goes wrong. However, if an app server deployment also requires a database deployment and we have to rollback I'm kind of at a loss. How can you rollback database schema changes without losing data? The only thing that I can think of is to write a script that will drop/revert tables/columns back to their original state. Is this really the best way?My company uses virtual machines for our web/ap