VÆLG fra underforespørgsel i Codeigniter Active Record

Det lykkedes mig at få forespørgslen til at virke ved at sætte from sub_query i den indledende select-sætning:

$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");