Rename a MySQL database used in a Rails Application

The safe and simple way to rename an existing database is to dump it out as SQL, create a new database with the new name and then load it back in.

$ mysqldump -u root -p -v old_db > old_db.sql
$ mysqladmin -u root -p create new_db
$ mysql -u root -p new_db < old_db.sql

If the database is the back end to a Rails app then you also need to update your config/database.yml file to use the new name and restart the web server, or nudge Passenger.

Test out the new DB, test it again, and then some more before destroying the old database.

$ mysqladmin -u root -p drop old_db