Masalah Penanganan Kesalahan Basis Data di CodeIgniter

Anda perlu mengeluarkan pengecualian jika ada kesalahan mysql:

try {
    $query_str = "SELECT * FROM tbl_user WHERE username = '".$username."'";
    $result = $this->db->query($query_str);

    if (!$result)
    {
      throw new Exception('error in query');
      return false;
    }        

    return $result;

} catch (Exception $e) {
    return;
}