Пользовательский интерфейс в codeigniter

на ваш взгляд

<form method = "post">
     <label>Type :</label>
     <select name = "rType">
        <option></option>
        <option value = "sum">SUM</option>
        <option value = "avg">AVG</option>
        <option value = "max">MAX</option>
     </select>
    <input type = "submit" value = "Fetch">
 </form>

в контроллере

$this->load->model("bank_query_model");
$rType = $this->input->post('rType');

$data["fetch_data"] = null;
if ($rType){
   $data["fetch_data"] = $this->bank_query_model->fetch_data($rType);
}
$this->load->view("bank_query_view", $data);

в модели

function fetch_data($rType)
{
    if ($rType == 'SUM'){
        $this->db->select("SUM(bank_balance) AS Bank_Balance");
        $this->db->from("bank_account");
        $query = $this->db->get();
    }
    elseif ($rType == 'AVG'){
        // Your query
        $query = '';
    }else{/*MAX*/
        // Your query
        $query = '';
    }

    return $query;
}