## 1
class ServicesUser < ActiveRecord::Base
  has_one :server
## 2
class Server < ActiveRecord::Base
  belongs_to :services_users
## Db
class AddServerNameToServicesUser < ActiveRecord::Migration
  def self.up
    add_column :services_users, :server_id, :integer
  end

  def self.down
    remove_column :services_users, :server_id
  end
end
## Script/console
>> ServicesUser.first.server
ActiveRecord::StatementInvalid: Mysql::Error: Unknown column 'servers.services_user_id' in 'where clause': SELECT * FROM `servers` WHERE (`servers`.services_user_id = 24)  LIMIT 1
[...]
## Problem
I wont fetch Server by server_id column in services_users table, NOT from services_user_id in servers table.