public function stat(string $table, string $column, array $where = [], array $order = []): ?array{
    if ( $this->check() ){
      return $this->rselect_all([
        'tables' => [$table],
        'fields' => [
          $column,
          'num' => 'COUNT(*)'
        ],
        'where' => $where,
        'order' => $order,
        'group_by' => [$column]
      ]);
    }
    return null;
  }