title: How to compare null in rails active record query
body: <p>How can I match null in rails active record.</p>
  
  <pre><code>User.where(['id = ? and active = ? and activation_code = ?', params[:id], 0, NULL]).first
  </code></pre>
  
  <p>or</p>
  
  <pre><code> User.where(['id = ? and active = ? and activation_code = ?', params[:id], 0, nil]).first
  </code></pre>
  
  <p>Both are not working.</p>