title: Rails: ActiveRecord Query for has_many :through model
body: <p>How to query for <em>Companies</em> with a certain <em>Branch</em> in a "has_many :through" relationship?</p>
  
  <pre><code>  #company.rb
    has_many :branch_choices
    has_many :branches, :through =&gt; :branch_choices
  </code></pre>
  
  <p>"Find all companies with Branch ID 3"</p>