event_id =1 och ditt användar-id =1
SELECT u.*
FROM wp_fd_subscriptions AS s
JOIN wp_fd_users AS u
ON s.event_user_id = u.id
LEFT JOIN wp_fd_matches m1
ON m1.event_id = s.event_id
AND m1.event_user_id = 1
AND m1.event_user_match_id = s.event_user_id
LEFT JOIN wp_fd_matches m2
ON m1.event_id = m2.event_id
AND m2.event_user_id = m1.event_user_match_id
AND m2.event_user_match_id = 1
WHERE s.event_id=1 AND u.id != 1 AND m2.id IS NULL;