title: Same enum values for multiple columns
body: <p>I need to do something like this:</p>
  
  <pre><code>class PlanetEdge &lt; ActiveRecord::Base
    enum :first_planet [ :earth, :mars, :jupiter]
    enum :second_planet [ :earth, :mars, :jupiter]
  end
  </code></pre>
  
  <p>Where my table is a table of edges but each vertex is an integer.</p>
  
  <p>However, it seems the abvove is not possible in rails. What might be an alternative to making string columns?</p>