mysql get max value and id
SELECT a.id, a.rev, a.contents
FROM YourTable a
INNER JOIN (
SELECT id, MAX(rev) rev
FROM YourTable
GROUP BY id
) b ON a.id = b.id AND a.rev = b.rev
get row from max
SELECT *
FROM t1 WHERE (id,rev) IN
( SELECT id, MAX(rev)
FROM t1
GROUP BY id
)