SELECT t1.`ПодпискаНаЮзера`
FROM `ТаблицаПодписокЮзеров` t1
LEFT JOIN (
SELECT DISTINCT `ПодпискаНаЮзера` AS `parent`
FROM `ТаблицаПодписокЮзеров`
WHERE `Юзер`=%d
) AS t2 ON t1.`Юзер`= t2.`parent`
WHERE t1.`Юзер`=%d OR t1.`Юзер`= t2.`parent`