protected function getSQL()
 {
     $sql = parent::getSQL();
     if ($sql === false) {
         return false;
     }
     $sql .= $this->getUpdateSql();
     return $sql;
 }
 public function __construct(AppConfig $config)
 {
     parent::__construct($config);
     $this->sql_cmd = 'REPLACE';
 }