title: Rails SQL Query with find
body: <p>I want this SQL query to be written in rails controller using find:</p>
  
  <pre><code>select id,name from questions
  where id not in (select question_id from levels_questions where level_id=15)
  </code></pre>
  
  <p>How will I do this? I am using Rails framework and MySQL.
  Thanks in advance.</p>