求高效SQL
基本信息表
CREATE TABLE `message` (
`id` int(1) NOT NULL auto_increment,
`title` varchar(128) default NULL,
PRIMARY KEY (`id`)
) ENGINE=MyISAM AUTO_INCREMENT=4 DEFAULT CHARSET=utf8;
基本信息的评论表
CREATE TABLE `comment` (
`cid` int(1) NOT NULL auto_increment,
`id` int(1) default NULL,
`msg` varchar(123) default NULL,
PRIMARY KEY (`cid`)
) ENGINE=MyISAM AUTO_INCREMENT=5 DEFAULT CHARSET=utf8;
现在要求查询message表里面。对应评论总数最多的2条记录。
我目前用group by这么实现了。同学说,如果不用group by 也有办法实现,但是我想不到。所以请求大家,有没有最高效的针对这个SQL的查询语句
select m.id,m.title,count(c.id) as cc from message m, comment c where m.id =c.id group by title order by cc desc limit 2;
------解决方案--------------------
select b.*
from (select id,count(*) from comment group by id order by 2 desc limit 2) a ,message b
where a.id=b.id