Install PHP and use phpMyAdmin.
Oracle SQL Developer works with MySQL, and is Java.
Did you check for anything MySQL might have for sale?
If you're going to be using ActiveRecord::Migrations, then there's
probably no need to have such a tool. Between migrations and the
rails script/console, there's really not a compelling reason to have
direct access to the database during normal development (well, you
might need a command line for fixing the schema_info.version when you
mess up a migration, but just don't screw up that badly 
-Rob
