PILIH dari subquery di Codeigniter Active Record

Saya berhasil membuat kueri berfungsi dengan meletakkan from sub_query ke dalam pernyataan pilih awal :

$this->db->select("*, 
  (select image_path from image where image_table = 'model' and image_table_id = model_id
  group by image_table_id limit 1) as ModelImg FROM 
  (SELECT * FROM $view where offer_table = 'derivative' order by offer_order) x");