UPDATE username SET cent = cent - val WHERE EXISTS (SELECT author, count( * ) * 5 AS val
FROM bbsthreads
WHERE tid
IN ( 3, 2, 1 ) AND username.username = bbsthreads.author
GROUP BY author
)
FROM bbsthreads
WHERE tid
IN ( 3, 2, 1 ) AND username.username = bbsthreads.author
GROUP BY author
)
FROM bbsthreads
WHERE tid
IN ( 3, 2, 1 )
GROUP BY author
) b
SET a.cent = a.cent - b.val WHERE a.username = b.author