MySQL group by和max返回错误的行

Question

我有两张桌子,我试着找到每天得分最高的"帖子".

CREATE TABLE IF NOT EXISTS `posts_points` (
  `post_id` int(10) unsigned NOT NULL,
  `comments` smallint(5) unsigned NOT NULL,
  `likes` smallint(5) unsigned NOT NULL,
  `favorites` smallint(5) unsigned NOT NULL,
   PRIMARY KEY (`post_id`)
) ENGINE=MyISAM DEFAULT CHARSET=utf8;


CREATE TABLE IF NOT EXISTS `posts` (
  `profile_id` int(10) unsigned NOT NULL,
  `post_id` int(10) unsigned NOT NULL,
  `pubdate_utc` datetime NOT NULL,
  PRIMARY KEY (`post_id`),
  KEY `profile_id` (`profile_id`),
) ENGINE=MyISAM DEFAULT CHARSET=utf8 ROW_FORMAT=DYNAMIC;

我已经尝试过以下查询.它返回正确的分数,但其他列只是随机行.我究竟做错了什么 ？

SELECT p.post_id, p.profile_id
   , MAX(t1.score)
   , DATE_FORMAT(t1.pubdate_utc, '%d %b') post_date
   , DATE(t1.pubdate_utc) mydate
FROM
(
   SELECT p.profile_id, p.post_id, p.pubdate_utc
      , (pp.comments + pp.likes + pp.favorites) AS score
   FROM posts p 
   INNER JOIN posts_points pp ON p.post_id = pp.post_id
) t1
INNER JOIN posts p ON t1.post_id = p.post_id
   AND t1.pubdate_utc = p.pubdate_utc
GROUP BY mydate
ORDER BY mydate DESC
LIMIT 18;

Answer 1

Column1  Column2
C        d
A        any thing
D        y
B        z  

如果您按 Column1 排序此数据，那么它看起来像这样 .....orderby 仅对第一列进行排序......

Column1  Column2
A        any thing
B        z            
C        d
D        y