CFile::UpdateExternalId

static function UpdateExternalId($ID, $external_id)
{
	global $DB;
	$external_id = trim($external_id);
	$DB->Query(
		"UPDATE b_file SET
			EXTERNAL_ID = ".($external_id != ""? "'".$DB->ForSql($external_id, 50)."'": "null").",
			TIMESTAMP_X = ".$DB->GetNowFunction()."
		WHERE ID=".intval($ID)
	);
	static::CleanCache($ID);
}