title: Codeigniter update_batch() with included update of the where key
body: <p>I want to update multiple rows in the database with codeigniters <code>update_batch()</code> function.<br>
  But the <strong>field specified in the where</strong> should also be changed.</p>
  
  <p>The following code should make it clear:</p>
  
  <pre><code>$set = array(
    array(
      'token'           =&gt; '65787131678754',
      'device'          =&gt; 'none',
      'new_token_value' =&gt; ''
    ),
    array(
      'token'           =&gt; '75798451315464',
      'device'          =&gt; 'none',
      'new_token_value' =&gt; ''
    )
  );
  
  $this-&gt;db-&gt;update_batch(TBL_NAME, $set, 'token');
  </code></pre>
  
  <p>Tokens specified in <code>token</code> should be updated with <code>device</code> to <code>'none'</code> and the <code>token</code> itself should be set to empty string <code>''</code>.</p>
  
  <p>Is this possible with <code>update_batch()</code> function?</p>
  
  <hr>
  
  <p>In sql I would write something like</p>
  
  <pre><code>UPDATE TBL_NAME
  SET token='', device='none'
  WHERE token='65787131678754'
  </code></pre>
  
  <p>for one update but this is not practicable for multiple, so I want to use the <code>update_batch()</code> function. </p>