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我正在为一个网站编写一个私人消息系统。用户可以与多个其他用户之一（包括他/她自己）进行通信。我有三张桌子

- users
- conversation_list
- conversation_messages

对于我的数据库，如下所示。

该users表包含所有用户

该conversation_messages表保存写入的消息，每条消息都有一个 conversation_id

保存每个对话中的conversation_list参与者列表

当然，每个对话都由唯一的标识conversation_id

现在，我希望从表中查询以下内容： 

- getInboxMessages <-- Difficult
    Get all new messages directed to a user. 
    Replies to a message should be grouped as a conversation 
    and the latest reply previewed
- getOutboxMessages
    Get all messages sent by the user. 
    Replies to messages should be grouped as a conversation 
    and only the latest reply previewed
- getConversation
    Each message with all replies
- isUnreadMessage
    Check if a message has been read or not
- getNumberOfUnreadMessages
    Get the number of unread messages

到目前为止我所做的如下所示。

getOutboxMessages, getConversation,isUnreadMessage并且getNumberOfUnreadMessages可以工作，尽管查询可能不是最佳的！我很难获得getInboxMessages.

我只能在收件箱中获取对话的第一个线程。任何其他线程（回复）都不会作为新消息出现，而是作为已发送消息（发件箱）出现。但是，对消息的任何回复（对话的一部分）都不会显示为新消息！

一个想法？热烈欢迎任何支持获取正确的 getInboxMessages 查询以及优化查询！

CREATE TABLE IF NOT EXISTS `conversation_list` (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `user_id` varchar(50) NOT NULL,
  `conversation_id` int(11) NOT NULL,
  `added_by` varchar(50) NOT NULL,
  `date_created` int(11) NOT NULL,
  `date_lastPost` int(11) NOT NULL,
  `date_lastView` int(11) NOT NULL,
  `status` tinyint(1) NOT NULL,
  UNIQUE KEY `id` (`id`)
) ENGINE=InnoDB  DEFAULT CHARSET=utf8;

CREATE TABLE IF NOT EXISTS `conversation_messages` (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `sender` varchar(50) DEFAULT NULL,
  `conversation_id` int(11) NOT NULL,
  `message` text NOT NULL,
  `date_created` int(11) NOT NULL,
  `status` tinyint(1) NOT NULL,
  UNIQUE KEY `id` (`id`)
) ENGINE=InnoDB  DEFAULT CHARSET=utf8;


CREATE TABLE IF NOT EXISTS `users` (
  `username` varchar(30) NOT NULL,
  `password` varchar(40) default NULL,
  `usersalt` varchar(8) NOT NULL,
  `userid` varchar(32) default NULL,
  `userlevel` tinyint(1) unsigned NOT NULL,
  `email` varchar(50) default NULL,
  `timestamp` int(11) unsigned NOT NULL,
  `regdate` int(11) unsigned NOT NULL,
  PRIMARY KEY  (`username`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;

查询

getInboxMessages
================
SELECT *
FROM conversation_messages AS m
JOIN
    (SELECT mx.conversation_id,
     MAX(mx.date_created) AS MaxTime
    FROM conversation_messages AS mx
    GROUP BY mx.conversation_id) AS mx ON m.conversation_id = mx.conversation_id
    AND m.date_created = mx.MaxTime
JOIN
    (SELECT mu.conversation_id
     FROM conversation_list AS mu
     WHERE mu.user_id = :subuser
     GROUP BY mu.conversation_id) AS mux ON m.conversation_id = mux.conversation_id
JOIN conversation_list AS mu ON m.conversation_id = mu.conversation_id
GROUP BY mu.conversation_id
ORDER BY m.date_created DESC

getOuboxMessages
================
SELECT *
FROM conversation_messages AS m

JOIN
    (SELECT mx.conversation_id,
     MAX(mx.date_created) AS MaxTime
     FROM conversation_messages AS mx
     GROUP BY mx.conversation_id) AS mx ON m.conversation_id = mx.conversation_id
AND m.date_created = mx.MaxTime

JOIN
    (SELECT mu.conversation_id, mu.user_id
     FROM conversation_list AS mu
     WHERE mu.added_by = :subuser
     GROUP BY mu.conversation_id) AS mux ON m.conversation_id = mux.conversation_id

JOIN conversation_list AS mu ON m.conversation_id = mu.conversation_id

ORDER BY m.date_created DESC

isUnreadMessage
===============
SELECT * FROM conversation_list WHERE date_created >= date_lastView AND conversation_id = :messageid AND user_id = :subuser

getConversation
===============
SELECT conversation_id, message, sender, date_created 
FROM conversation_messages 
WHERE conversation_id = :submessage_id 
ORDER BY date_created DESC

getNumberOfUnreadMessages
=========================
SELECT l.conversation_id, count(*)
FROM   conversation_list l
JOIN   conversation_messages m ON m.conversation_id = l.conversation_id AND m.date_created >= l.date_lastview
WHERE  l.user_id = :subuser
GROUP BY l.conversation_id
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