public function findByCompany($id)
 {
     $S_sql = 'SELECT * FROM subgroup WHERE company_id = ?';
     $A_params = array($id);
     $O_connection = new Connection();
     if ($A_subgroup = $O_connection->requestDb($S_sql, $A_params, self::CLASS_NAME)) {
         $A_subgroups = array();
         foreach ($A_subgroup as $O_subgroup) {
             $O_companyMapper = new CompanyMapper();
             $O_company = $O_companyMapper->findById($id);
             $O_subgroup->setCompany($O_company);
             $A_subgroups[] = $O_subgroup;
         }
         return $A_subgroup;
     } else {
         throw new Exception("une erreur c'est produite lors de la requĂȘte findByCompany");
     }
 }