exactly what does rake db:migrate do?

Question

Does rake db:migrate only add new migrations, or does it drop all migrations/changes and build everything new?

I think rake is throwing an error because it is trying to

Answer 1

A migration means that you move from the current version to a newer version (as is said in the first answer). Using rake db:migrate you can apply any new changes to your schema. But if you want to rollback to a previous migration you can use rake db:rollback to nullify your new changes if they are incorrectly defined. Caution: by doing so your data will be lost.