How do I run a migration again, without deleting all the newer migrations?

rake db:migrate:up VERSION=20090408054532

this will migrate all file upto VERSION=20090408054532

checkout Run a single migration file

Thanks for the help everyone. This is what worked for me:

WARNING: these commands will delete all data in your database!

rake db:drop
rake db:create
rake db:migrate

If you are developing locally and it wouldn't hurt to remove all data from your models you could simply drop your db and then create & migrate from scratch:

Purge or recreate a Ruby on Rails database

It will run the down and then the up step (This command can drop your table!):

rake db:migrate:redo VERSION=xxxxxxx

To prevent your table from being deleted you could do this in conjunction with commenting out the down step temporarily.