USE lastfm

CREATE TEMPORARY TABLE users_having_a_badge (SELECT username, 0 AS has_a_badge FROM users) ;
CREATE TEMPORARY TABLE badges_having_a_user (SELECT username, 0 AS has_a_user FROM badges) ;

UPDATE users_having_a_badge, badges SET has_a_badge = 1 WHERE users_having_a_badge.username = badges.username ;
UPDATE badges_having_a_user, users SET has_a_user = 1 WHERE badges_having_a_user.username = users.username ;

DELETE users.* FROM users, users_having_a_badge where has_a_badge = 0 AND users.username = users_having_a_badge.username ;
SELECT badges.png FROM badges, badges_having_a_user where has_a_user = 0 AND badges.username = badges_having_a_user.username ;
DELETE badges.* FROM badges, badges_having_a_user where has_a_user = 0 AND badges.username = badges_having_a_user.username ;

DROP TABLE users_having_a_badge;
DROP TABLE badges_having_a_user;