SELECT * FROM (
SELECT * FROM users_data WHERE private='0'
UNION
SELECT * FROM deleted WHERE private='0'
UNION
SELECT * FROM mails WHERE private='0'
) u;
SELECT * FROM users_data WHERE private='0' UNION SELECT * FROM deleted WHERE private='0' UNION SELECT * FROM mails WHERE private='0'
SELECT * FROM users_data, deleted, mails WHERE users_data.private='0' AND deleted.private='0' AND mails.private='0'