簡單的mysql查詢以特定的順序顯示結果

Question

我創建了2個表消息和對話。

對話表將爲兩個正在發送和接收消息的用戶創建一個唯一的ID。

消息表將包含用戶消息的所有信息。

會話表

conversation_id | user_id1 | user_id2 |last_message_id 
     1    5   1   4 
     2    5   2   5 

message_id | conversation_id | sender_id | message | created_time 
    1   1     5   MSG A  2012-06-10 00:20:04 
    2   1     5   MSG B  2012-06-10 00:20:21 
    3   1     5   MSG C  2012-06-10 00:21:09 
    4   1     1   MSG D  2012-06-10 00:22:23 
    5   2     5   MSG E  2012-06-10 00:25:16 

輸出我想：

sender_id | message | created_time 
    5  MSG E  2012-06-10 00:25:16 
    1  MSG D  2012-06-10 00:22:23 

我試了一下：

SELECT * FROM conversation c, messages m 
WHERE c.user_id1='$userid' OR c.user_id2='$userid' 
AND c.last_message_id=m.message_id 
ORDER BY created_time DESC 

但THI s查詢不顯示正確的結果。

我們是否需要像下面這樣的東西來分組？

SELECT * FROM TABLE 
WHERE CONDITION 
(SELECT MAX(created_time) 
FROM TABLE 
GROUP BY SOMEFEILD) 
order by time desc 

Answer 1

試圖改變你這樣的查詢

SELECT * FROM conversation c, messages m 
WHERE (c.user_id1='$userid' OR c.user_id2='$userid') 
AND c.last_message_id=m.message_id 
ORDER BY created_time DESC