title: Activerecord query .where string as number
body: <p>I have record in my db where there is a time element which is a number stored as a string. 
  I'd like to run a where query where I check if the number is greater than x
  e.g. </p>
  
  <pre><code>Recording.where("recording_duration_ms.to_i &gt; 60000")
  </code></pre>
  
  <p>Sure it must be simple to do...</p>