How to delete migration files in Rails 3

Another way to delete the migration:

$ rails d migration SameMigrationNameAsUsedToGenerate

Use it before rake db:migrate is executed because changes in database will stay forever :) - or remove changes in Database manually

You can also run a down migration like so:

rake db:migrate:down VERSION=versionnumber

Refer to the Ruby on Rails guide on migrations for more info.

I usually:

1. Perform a rake db:migrate VERSION=XXX on all environments, to the version before the one I want to delete.
2. Delete the migration file manually.
3. If there are pending migrations (i.e., the migration I removed was not the last one), I just perform a new rake db:migrate again.

If your application is already on production or staging, it's safer to just write another migration that destroys your table or columns.

Another great reference for migrations is: http://guides.rubyonrails.org/migrations.html

Run below commands from app's home directory:

1. rake db:migrate:down VERSION="20140311142212" (here version is the timestamp prepended by rails when migration was created. This action will revert DB changes due to this migration)

2. Run "rails destroy migration migration_name" (migration_name is the one use chose while creating migration. Remove "timestamp_" from your migration file name to get it)