title: How to use 'DISTINCT' in Codeigniter Active Records?
body: <p>I have a query using active records.</p>
  
  <pre><code>$this-&gt;db-&gt;select('reg.users_id,reg.registration_id,reg.device_type');
  $this-&gt;db-&gt;join('users as usr','usr.users_id = reg.users_id','left');
  $this-&gt;db-&gt;where('usr.users_status',1);
  $this-&gt;db-&gt;where('reg.users_id',91);
  $query = $this-&gt;db-&gt;get('users_gcm_registration as reg');
  </code></pre>
  
  <p>I want to fetch <code>DISTINCT(registration_id)</code>.</p>
  
  <p>How can I do that?</p>