获取select查询中表的最后一条记录

Question

这是对最后一条记录插入到选择查询中的另一个问题的跟进

我正在尝试编辑一个查询,Andrea非常友好地帮助我昨天哪个页面工作正常,但我试图创建一个类似的查询,没有太多的运气.

我需要的是每个电路板显示电路板名称,与该电路板相关的主题和消息的数量以及最后一条消息的用户,主题和日期(确实有效)

我需要的是获取董事会名称,主题和消息计数

这是我的表结构

CREATE TABLE `boards` (
  `boardid` int(2) NOT NULL auto_increment,
  `boardname` varchar(255) NOT NULL default '',
  PRIMARY KEY  (`boardid`)
);

CREATE TABLE `messages` (
  `messageid` int(6) NOT NULL auto_increment,
  `topicid` int(4) NOT NULL default '0',
  `message` text NOT NULL,
  `author` varchar(255) NOT NULL default '',
  `date` datetime(14) NOT NULL,
  PRIMARY KEY  (`messageid`)
);

CREATE TABLE `topics` (
  `topicid` int(4) NOT NULL auto_increment,
  `boardid` int(2) NOT NULL default '0',
  `topicname` varchar(255) NOT NULL default '',
  `author` varchar(255) NOT NULL default '',
  PRIMARY KEY  (`topicid`)
);

以及我根据Andrea为我做的查询得出的查询.这个查询在boardname中输出的内容,主题和消息的数量(即使有5个也是1),主题作者和messagecount(不需要),作者和上一篇文章的日期(需要) )但不是所需的主题名称

SELECT b.boardname, count( DISTINCT t.topicname ) AS topics, count( lm.message ) AS message, t.author as tauthor, 

      (select count(message) from messages m where m.topicid = t.topicid) AS messagecount, 
       lm.author as lauthor, lm.date
  FROM topics t
  INNER JOIN messages lm
    ON lm.topicid = t.topicid AND lm.date = (SELECT max(m2.date) from messages m2)
  INNER JOIN boards b
    ON b.boardid = t.boardid
  GROUP BY t.topicname

这是我的原始查询,它做了我想要的但得到了第一篇文章,而不是最后一篇

SELECT b.boardid, b.boardname, count( DISTINCT t.topicname ) AS topics, count( m.message ) AS message, m.author AS author, m.date AS date, t.topicname AS topic
FROM boards b
INNER JOIN topics t ON t.boardid = b.boardid
INNER JOIN messages m ON t.topicid = m.topicid
INNER JOIN (

SELECT topicid, MAX( date ) AS maxdate
FROM messages
GROUP BY topicid
) test ON test.topicid = t.topicid
GROUP BY boardname
ORDER BY boardname

任何帮助与此非常赞赏

Answer 1

您需要根据ORDER BY子句定义"LAST".完成后,您可以撤消订单的方向并添加LIMIT 1到查询中.