Создание БД, настройка INDEX и некоторые запросы.

SELECT u.NAME FROM users AS u INNER JOIN subscriptions AS s ON u.id = s.user_id INNER JOIN magasins AS m ON m.id = s.magasin_id WHERE ((YEAR(CURRENT_DATE)-YEAR(u.date_birth)) - (RIGHT(CURRENT_DATE, 5) < RIGHT(u.date_birth, 5))) >= 30 AND m.NAME = 'Мурзилка' AND s.subscribe = 1;

SELECT * FROM users WHERE id = round(1 + rand() * (SELECT count(*) FROM users)) LIMIT 1;