If you want to run rails on your local machine and you already have XAMPP installed, then you propably want to use your mysql installation that comes with XAMPP. Here´s a short description, how to do that.

First you need to tell the mysql gem the path to your files installed with XAMPP. This can be achieved by setting some flags during gem install:

sudo env ARCHFLAGS="-arch i386" gem install mysql -- --with-mysql-dir=/Applications/XAMPP/xamppfiles/lib/mysql --with-mysql-lib=/Applications/XAMPP/xamppfiles/lib/mysql/ --with-mysql-include=/Applications/XAMPP/xamppfiles/include/mysql/

After that, you can adjust your database.yml from your rails app:

development:
  adapter: mysql2
  encoding: utf8
  database: your_db
  pool: 5
  username: root
  password:
  socket: /Applications/XAMPP/xamppfiles/var/mysql/mysql.sock

Finally, run bundle in the rails project again and it should work.