$this->db->from('files');        

$this->db->where_in('file_id', $file_id);         

$orderby = "field('file_id',$id)"; 

$this->db->order_by($orderby,'',false);

->>

SELECT * FROM (`files`) WHERE `file_id` IN ('685', '680', '679') ORDER BY field('file_id', `'685'`, `'680'`, `'679')`

order by절에 false를 줫음에도 밴틱문자열? 이 들어오는데요 .. 어떻게 해야하죠?