mysql分组 排序取每条记录中最后更新记录

CREATE TABLE IF NOT EXISTS `test` (
`id` int(10) unsigned NOT NULL auto_increment,
`install` int(10) unsigned NOT NULL,
`day` int(10) unsigned NOT NULL,
`aid` int(10) unsigned NOT NULL,
PRIMARY KEY (`id`)
) ENGINE=MyISAM DEFAULT CHARSET=utf8 AUTO_INCREMENT=12 ;

INSERT INTO `test` (`id`, `install`, `day`, `aid`) VALUES
(1, 1232, 20080808, 1),
(2, 2321, 20080809, 2),
(3, 1236, 20080810, 3),
(5, 4212, 20080809, 1),
(6, 2312, 20080810, 1),
(7, 1432, 20080811, 1),
(8, 2421, 20080808, 2),
(9, 4245, 20080811, 2),
(10, 5654, 20080810, 2),
(11, 412, 20080808, 3);

SELECT A.* FROM test A,
(SELECT aid, MAX(day) max_day FROM test GROUP BY aid) B
WHERE A.aid = B.aid AND A.day = B.max_day
ORDER BY a.install DESC

drop procedure set_rank;
 create procedure set_rank()
 begin
 set @i=1;
 set @number=(select count(1) from suppliers_performance);
 update suppliers_performance set score_rank=0;
 
 while @i<@number
 do
 begin
     update suppliers_performance set score_rank=@i where id in (select id from (select id from suppliers_performance where score_rank=0 order by score limit 1) b);
     set @i=@i+1;
 end;
 end WHILE;
 end;