在线程中获取最新消息

Question

我有一个查询,获取消息传递系统的主页所需的所有信息(包括未读消息计数等)...但它当前检索原始线程消息.我想扩充以下查询以获取每个线程中的最新消息.

这个查询非常接近,但是我平庸的SQL技能让我无法完成任务......

$messages = array();
$unread_messages_total = 0;

$messages_query = "
SELECT m.*
    , COUNT(r.id) AS num_replies
    , MAX(r.datetime) AS reply_datetime
    , (m.archived NOT LIKE '%,".$cms_user['id'].",%') AS message_archive
    , (m.viewed LIKE '%,".$cms_user['id'].",%') AS message_viewed 
    , SUM(r.viewed NOT LIKE '%,".$cms_user['id'].",%') AS unread_replies 
    , CASE
        WHEN MAX(r.datetime) >= m.datetime THEN MAX(r.datetime)
        ELSE m.datetime
        END AS last_datetime
FROM directus_messages AS m
LEFT JOIN directus_messages as r ON m.id = r.reply
WHERE m.active = '1'  
AND (m.to LIKE '%,".$cms_user['id'].",%' OR m.to = 'all' OR m.from = '".$cms_user['id']."') 
GROUP BY m.id
HAVING m.reply = '0' 
ORDER BY last_datetime DESC";

foreach($dbh->query($messages_query) as $row_messages){
    $messages[] = $row_messages;
    $unread_messages_total += (strpos($row_messages['archived'], ','.$cms_user['id'].',') === false && ( (strpos($row_messages['viewed'], ','.$cms_user['id'].',') === false && $row_messages['unread_replies'] == NULL) || ($row_messages['unread_replies']>0 && $row_messages['unread_replies'] != NULL) ) )? 1 : 0;
}

提前感谢您提供的任何帮助!

编辑:(数据库)

CREATE TABLE `cms_messages` (
  `id` int(10) NOT NULL auto_increment,
  `active` tinyint(1) NOT NULL default '1',
  `subject` varchar(255) NOT NULL default '',
  `message` text NOT NULL,
  `datetime` datetime NOT NULL default '0000-00-00 00:00:00',
  `reply` int(10) NOT NULL default '0',
  `from` int(10) NOT NULL default '0',
  `to` varchar(255) NOT NULL default '',
  `viewed` varchar(255) NOT NULL default ',',
  `archived` varchar(255) NOT NULL default ',',
  PRIMARY KEY  (`id`)
) ENGINE=MyISAM AUTO_INCREMENT=1 DEFAULT CHARSET=latin1;

编辑2 :(要求)

• 返回特定的 所有父消息user_id:$cms_user['id']
• 返回该父消息的回复数: num_replies
• 返回该父消息的未读回复数:unread_replies
• 返回父邮件的日期或最近的回复: last_datetime
• 返回消息是否在存档中: message_archive
• 返回是否已查看邮件: message_viewed
• 以DESC日期时间顺序返回所有消息
• 返回最新的message,来自父母或回复,如果有一些(如gmail)

Answer 1

如果您只有2个级别的消息(即只有父消息和直接答案),您可以尝试以下查询:

select
    root_message.id,
    root_message.active,
    root_message.subject,
    case
        when max_reply_id.max_id is null then 
            root_message.message
        else
            reply_message.message
    end as message,
    root_message.datetime,
    root_message.reply,
    root_message.from,
    root_message.to,
    root_message.viewed,
    root_message.archived
from
    -- basic data
    cms_messages as root_message
    -- ID of last reply for every root message
    left join (
        select 
            max(id) as max_id, 
            reply as parent_id 
        from 
            cms_messages
        where
            reply <> 0 
        group by 
            reply
    ) as max_reply_id on max_reply_id.parent_id = root_message.id                                              
    left join cms_messages as reply_message on reply_message.id = max_reply_id.max_id
where
    root_message.reply = 0

它使用子查询max_reply_id作为数据源来选择最新答案的ID.如果存在(即,如果有答案),reply_message.message则使用.如果它不存在(没有找到根消息的答案),则root_message.message使用.

你还应该考虑表格的结构.例如,如果reply包含NULL,如果是父消息或现有消息的ID,则更有意义.目前,您将其设置为0(不存在的消息的ID),这是错误的.类型viewed和archived也很奇怪.

编辑:您还应该避免使用having子句.使用where替代,可能的情况下.

这是一个应该满足您要求的新查询.如果它有任何问题(即,如果它返回错误的数据),请告诉我.

像第一个查询一样,它:

• 使用子查询reply_summary来累积有关回复的数据(最后回复的ID,回复的数量和未读回复的数量);
• 将此子查询连接到基表;
• 连接cms_messages as reply_message到子查询,基于reply_summary.max_reply_id,获取有关上一个回复(消息,日期时间)的数据.

我已经简化了你如何确定的方式last_datetime- 它现在需要最后一次回复的时间(如果有任何回复),或原始帖子的时间(没有找到回复时).

我没有过滤回复from和to字段.如果有必要,应更新子查询的where子句reply_summary.

select
    parent_message.id,
    parent_message.subject,
    parent_message.message,
    parent_message.from,
    parent_message.to,
    coalesce(reply_summary.num_replies, 0) as num_replies,
    last_reply_message.datetime as reply_datetime,
    (parent_message.archived NOT LIKE '%,{$cms_user['id']},%') AS message_archive,
    (parent_message.viewed   LIKE     '%,{$cms_user['id']},%') AS message_viewed,
    reply_summary.unread_replies,
    coalesce(last_reply_message.message, parent_message.message) as last_message,
    coalesce(last_reply_message.datetime, parent_message.datetime) as last_datetime
from
    cms_messages as parent_message
    left join (
        select
            reply as parent_id,
            max(id) as last_reply_id,
            count(*) as num_replies,
            sum(viewed not like '%,{$cms_user['id']},%') as unread_replies
        from
            cms_messages
        where
            reply <> 0 and
            active = 1
        group by
            reply
    ) as reply_summary on reply_summary.parent_id = parent_message.id
    left join cms_messages as last_reply_message on last_reply_message.id = reply_summary.last_reply_id
where
    parent_message.reply = 0 and
    parent_message.active = 1 and
    (parent_message.to like '%,{$cms_user['id']},%' or parent_message.to = 'all' or parent_message.from = '{$cms_user['id']}')
order by
    last_datetime desc;