title: ActiveRecord None Key Association
body: <p>I have two tables/models (User, Demographic) which have a loose relationship and share a common column (email). There could be more than one User record with the same email, but there would only be a single demographic record.</p>
  
  <p>Is it possible to define a has_one and has_many relationship and force it to use the email column for the join instead of id? </p>
  
  <p>Thanks,
  Scott</p>
  
  <p>P.S. If it matters, I am using ActiveRecord 3.x</p>