SELECT * FROM ttw a WHERE
(a.`event_id`=7 AND a.`event_type`=2)
OR
EXISTS (SELECT 1 FROM ttw WHERE a.id=`id`-1 AND `event_id`<>7 AND `event_type`<>2 )
;
加入自增ID
SELECT * FROM ttw a WHERE a.`event_id`=7 AND a.`event_type`=2
UNION
SELECT b.* FROM ttw a
LEFT JOIN ttw b ON (a.id=b.`id`-1 )
WHERE a.`event_id`=7 AND a.`event_type`=2 ORDER BY ID;