For whatever reason, you might just need to transition your Rails app's content from one database type to another (or even just to a new database with the same adapter). I've found that yaml_db does a great job helping you with this task.
The first thing to do is get
$ bundle install
To dump the data, just run the appropriate rake task.
$ bundle exec rake db:data:dump
Then, switch your database over to the new database. Note: If you're switching adapters, make sure you have the appropriate gem(s) installed.
You'll need to make sure your database is setup. If it isn't, then get on it!
$ bundle exec rake db:create $ bundle exec rake db:migrate
And then you can bring the data into the new database.
$ bundle exec rake db:data:load
Nice and easy! Be sure to note that if you're doing this to move content, then you may need to go through additional steps to move any uploaded assets.