Question

我是一个用户发送消息的平台。可以进行群组对话。

我的thread_members表：

id | user_id | thread_id 
------------------------- 
 1 |    1    |     1   
------------------------- 
 2 |    2    |     1  
------------------------- 
 3 |    1    |     2  
------------------------- 
 4 |    2    |     2  
------------------------- 
 5 |    3    |     2  
------------------------- 
 6 |    1    |     3  
------------------------- 
 7 |    3    |     3  
------------------------- 
 8 |    4    |     3

当我发送消息时，我想检查该线程是否已经存在。

让我们说：user_id＆＃39; 1＆＃39;向user_id＆＃39; 2＆＃39;

发送消息

结果应该是thread_id＆＃39; 1＆＃39;

应该是单个查询

修改

感谢大家，但我想我得到了答案：我现在没有遇到任何问题...

在PHP中：

$senderId = $_POST['sender']; // integer
$receiverIds = $_POST['receivers']; // array

$query = "SELECT thread_members.*, COUNT(*) 
          FROM thread_members 
          JOIN (   
            SELECT *, COUNT(*)   
            FROM (     
              SELECT *     
              FROM thread_members     
              WHERE user_id = " . $senderId . " "; 

              foreach ($receiverIds as $receiverId) 
              {
                $query .= " OR user_id = " . $receiverId . " ";  
              }

              $query .= " ) AS thread_members 
            GROUP BY thread_id 
            HAVING COUNT(*) = " . (count($receiverIds) + 1) . "
            ORDER BY COUNT(*) 
          ) AS thread_members_copy ON thread_members.thread_id = thread_members_copy.thread_id 
          GROUP BY thread_members.thread_id 
          HAVING COUNT(*) = " . (count($receiverIds) + 1) . "
          ORDER BY COUNT(*) ";

(count($receiverIds) + 1)都是接收者+发件人

Answer 1

您可以进行自我加入，然后检查包含两个用户ID值的记录：

SELECT t1.thread_id FROM
thread_members t1 INNER JOIN thread_members t2
ON t1.thread_id = t2.thread_id
WHERE t1.user_id = 1 AND t2.user_id = 2

检查群组对话中是否已存在线程

修改

1 个答案: