final public static function exists($keys): bool {
		
		// initialize some vars
		$db			= Database::getInstance();
		$tableKey	= (array)static::TABLE_KEY;
		$conds		= array();

		foreach ($tableKey as $field) {
			$conds[] = $field . ' = ?';
		}
		
		$query = 'SELECT COUNT(1) FROM `' . static::TABLE_NAME . '` WHERE ' . implode(' AND ', $conds);
		
		// execute and return value
		return (bool)Database::load($query, (array)$keys, PAIR_DB_COUNT);
		
	}