specialite v 0.1

 function getNonChoisi($cin){

             
       $res= $this->db      
       ->where('cin',$cin)->from('specialite')
            ->join('choix_candidats',' specialite.code_specialite !=choix_candidats.code_specialite','full')->get();
       
        return $res->result();
    }

this function is not valide it gets all the specialities !! 
we should use 'not in' unstade of '!=' i think but how ?