Migrating data and schema

Evolving your database schema without a sweat. Before you know it, you’ll have data that you care about in your application. Which makes adding, removing, or changing the schema an error-prone, time-consuming, and frustrating process. That is, unless you’re using Ruby on Rails. In 20 minutes, you’ll learn all about how database migrations can make your schema as flexible as your code with no fear of data loss.

http://media.rubyonrails.org/video/migrations.mov