How to rollback just one step using rake db:migrate

For starters

rake db:rollback will get you back one step

then

rake db:rollback STEP=n

Will roll you back n migrations where n is the number of recent migrations you want to rollback.

More references here.

Roll back the most recent migration:

rake db:rollback

Roll back the n most recent migrations:

rake db:rollback STEP=n

You can find full instructions on the use of Rails migration tasks for rake on the Rails Guide for running migrations.

Here's some more:

• rake db:migrate - Run all migrations that haven't been run already
• rake db:migrate VERSION=20080906120000 - Run all necessary migrations (up or down) to get to the given version
• rake db:migrate RAILS_ENV=test - Run migrations in the given environment
• rake db:migrate:redo - Roll back one migration and run it again
• rake db:migrate:redo STEP=n - Roll back the last n migrations and run them again
• rake db:migrate:up VERSION=20080906120000 - Run the up method for the given migration
• rake db:migrate:down VERSION=20080906120000 - Run the down method for the given migration

And to answer your question about where you get a migration's version number from:

The version is the numerical prefix on the migration's filename. For example, to migrate to version 20080906120000 run

$ rake db:migrate VERSION=20080906120000

(From Running Migrations in the Rails Guides)

Best way is running Particular migration again by using down or up(in rails 4. It's change)

rails db:migrate:up VERSION=timestamp

Now how you get the timestamp.Go to this path

/db/migrate

Identify migration file you want to revert.pick the timestamp from that file name.