Question

我正在开发一个带有两个表的消息传递系统和另一个包含用户信息的表对话可以在2个或更多用户之间。每个会话都有一个UID，用户之间交换的每条消息都标有该会话UID。

以下是表格：

conversation_list：此表格中的每一行都会链接user_id和conversation_id，它还包含用户上次查看对话的时间。

`id`                 -> unique ID, autoincremented
`user_id`            -> This contains the user associated with the conversation.
`conversation_id`    -> This contains the UID of the conversation
`date_lastView`      -> This field has the time that the user viewed the conversation last

conversation_messages：此表格中的每一行都包含一条消息

`id`                 -> unique ID, autoincremented
`user_id`            -> This contains the user that sent the message.
`conversation_id`    -> This contains the UID of the conversation
`date_created`       -> This contains the time when the message was posted
`message`            -> This contains the message

users：此表格中的每一行都包含一个用户

`User_ID`            -> UID of the user
`FirstName`          -> This contains the first name of the user
`LastName`           -> This contains the last name of the user

我已经有一个SQL查询来获取每个会话的最后一条消息。这是：

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 = :USER_ID_CONNECTED
   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

我现在想为这个完美工作的查询添加返回的能力：

每次会话的未读邮件数（所有邮件的数量都比登录用户的date_creaded大{/ 1}}
一个数组，其中包含每个对话中每个用户的date_lastView，并按照他们上次在对话中发布消息的时间排序。
对最后一个数组的想法与用户的User_ID和FirstName相同。

我尝试了一些事情，但我确实没有成功，所以我现在要求SO社区提供宝贵的帮助。

所有这些只能显示登录用户参与的对话。

它有帮助，我创建了一个SQLFiddle

Answer 1

用户对话中的未读邮件数量（此处为用户＃6）：

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 = 6
GROUP BY l.conversation_id

上次活动订购的对话参与者：

SELECT conversation_id, user_id, max(date_created) as last_active
FROM   conversation_messages
GROUP BY conversation_id, user_id
ORDER BY conversation_id, last_active

第三个查询应该与第二个查询一样，只需加入user_id上的另一个表，对吗？

Answer 2

我对the query to fetch the unread messages添加了3项改进：

如果last_view字段为空，则假定该用户从不检查他的消息，因此所有消息都将是“未读”
将新消息标识为非用户创建的消息。
如果没有未读消息，则计数将返回0

SELECT l.conversation_id, count(m.id)
FROM   conversation_list l
LEFT JOIN   conversation_messages m ON m.conversation_id = l.conversation_id AND (l.date_lastview IS NULL OR m.date_created > l.date_lastview)  AND m.user_id != 6
WHERE  l.user_id = 6
GROUP BY l.conversation_id

消息系统查询以获取最后的消息，未读消息的数量和对话中的用户数组

2 个答案: