Код: Выделить всё
DELETE FROM phpbb_acl_groups WHERE group_id = (SELECT group_id FROM phpbb_groups WHERE group_name = 'GUESTS');
DELETE FROM phpbb_acl_users WHERE user_id = (SELECT user_id FROM phpbb_users WHERE group_id = (SELECT group_id FROM phpbb_groups WHERE group_name = 'GUESTS'));
UPDATE phpbb_users SET user_permissions = '' WHERE group_id = (SELECT group_id FROM phpbb_groups WHERE group_name = 'GUESTS');