title: Activerecord select columns from a triple join query
body: <p>I have 3 models <code>Passenger, Taxi, Order</code> i want to get a certain column of these tables. I used this to join them successfully.</p>
  
  <pre><code>Taxi.joins(:orders =&gt; :passenger).where(:taxi =&gt;{:taxi_id =&gt;2 } )
  </code></pre>
  
  <p>I want to select some of the columns of passenger table and some of the column of order,
  but i do not know how can i do that?</p>
  
  <p>The other problem is that, the result of this query is only columns of Taxi and not the column of <code>taxi+order+passenger</code></p>
  
  <p>I think i have a problem with my query</p>