Example for connecting RoR to a MAMP hosted database. Socket path assumes MAMP has been installed in the default directory. DATABASE_NAME, USERNAME, and PASSWORD will need to be replaced with the appropriate values from the database in MAMP. Default username and password are both root.

database.yml

development:
  adapter: mysql2
  database: DATABASE_NAME
  username: USERNAME
  password: PASSWORD
  socket: /Applications/MAMP/tmp/mysql/mysql.sock
  host: localhost
  pool: 5
  timeout: 5000
  encoding: utf8