Php MySQL查询，按分组，然后按最新分组条件排序

我有一段代码，它根据登录用户的ID对消息进行分组，代码工作得很好。但现在我想做一些修改，我不知道如何实现

我的查询代码

及

---

有什么帮助吗？

我在where子句中添加了这一点，它似乎起作用了

WHERE 
'$myid' IN ( senderID ) AND senderdelete = 0 
OR
'$myid' IN ( receiverID ) AND receiverdelete = 0 

完整更新代码

 $query_messages = mysqli_query($link,"SELECT 
      PreQuery.*,
      m2.message,
      m2.senderID,
      m2.receiverID,
      m2.senderdelete,
      m2.receiverdelete
   from
      ( SELECT 
              if( m.senderID < m.receiverID, m.senderID, m.receiverID ) as Person1,
              if( m.senderID < m.receiverID, m.receiverID, m.senderID ) as Person2,
              max( m.messageID ) as LastMessageIDPerChat,
              max( m.date ) as LastMessageDate
           FROM 
              messages m
           WHERE 
                   '$myid' IN ( senderID) AND senderdelete = 0 OR '$myid' IN ( receiverID) AND receiverdelete = 0 

           GROUP BY
              Person1, 
              Person2
           ORDER BY 
              m.date ASC
           LIMIT 10 ) PreQuery

         JOIN messages m2
            on PreQuery.LastMessageIDPerChat = m2.messageID    ORDER BY 
              date DESC");
$row_messages = mysqli_fetch_assoc($query_messages);
$totalRows_messages = mysqli_num_rows($query_messages);

---

我在where子句中添加了这一点，它似乎起了作用

WHERE 
'$myid' IN ( senderID ) AND senderdelete = 0 
OR
'$myid' IN ( receiverID ) AND receiverdelete = 0 

完整更新代码

 $query_messages = mysqli_query($link,"SELECT 
      PreQuery.*,
      m2.message,
      m2.senderID,
      m2.receiverID,
      m2.senderdelete,
      m2.receiverdelete
   from
      ( SELECT 
              if( m.senderID < m.receiverID, m.senderID, m.receiverID ) as Person1,
              if( m.senderID < m.receiverID, m.receiverID, m.senderID ) as Person2,
              max( m.messageID ) as LastMessageIDPerChat,
              max( m.date ) as LastMessageDate
           FROM 
              messages m
           WHERE 
                   '$myid' IN ( senderID) AND senderdelete = 0 OR '$myid' IN ( receiverID) AND receiverdelete = 0 

           GROUP BY
              Person1, 
              Person2
           ORDER BY 
              m.date ASC
           LIMIT 10 ) PreQuery

         JOIN messages m2
            on PreQuery.LastMessageIDPerChat = m2.messageID    ORDER BY 
              date DESC");
$row_messages = mysqli_fetch_assoc($query_messages);
$totalRows_messages = mysqli_num_rows($query_messages);

---

为了避免将来出现歧义，特别是在扩展的复杂条件下，请尝试包装，例如“$user'=senderID和senderdelete=0或“$user'=receiverID和receiverdelete=0，我将在我的程序@DRapp中使用这些更改。我非常支持避免将来出现歧义，特别是在扩展的复杂条件下，尝试包装，例如“$user'=senderID和senderdelete=0或“$user'=receiverID和receiverdelete=0。我将在我的程序@DRapp中使用这些更改。我非常感谢这些支持

 $query_messages = mysqli_query($link,"SELECT 
      PreQuery.*,
      m2.message,
      m2.senderID,
      m2.receiverID,
      m2.senderdelete,
      m2.receiverdelete
   from
      ( SELECT 
              if( m.senderID < m.receiverID, m.senderID, m.receiverID ) as Person1,
              if( m.senderID < m.receiverID, m.receiverID, m.senderID ) as Person2,
              max( m.messageID ) as LastMessageIDPerChat,
              max( m.date ) as LastMessageDate
           FROM 
              messages m
           WHERE 
                   '$myid' IN ( senderID) AND senderdelete = 0 OR '$myid' IN ( receiverID) AND receiverdelete = 0 

           GROUP BY
              Person1, 
              Person2
           ORDER BY 
              m.date ASC
           LIMIT 10 ) PreQuery

         JOIN messages m2
            on PreQuery.LastMessageIDPerChat = m2.messageID    ORDER BY 
              date DESC");
$row_messages = mysqli_fetch_assoc($query_messages);
$totalRows_messages = mysqli_num_rows($query_messages);