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我正在制作一个小型网络应用程序来发送短信。我必须向用户展示他们最后发送的短信（如 Android、iOS 中的短信应用......）

我的三张桌子：

---------   -----------   -----------
| users |   |  sms    |   | indexes |
---------   -----------   -----------
   id           id            id
   ..         user_id       user_id
              receiver      phone_n
             created_at      name

我已经发出了一个 SQL 请求，以获取按索引表的名称/电话号码分组的最后发送的 SMS：

SELECT S.receiver, S.message, I.name, temp.last_sent, I.id
FROM sms S
INNER JOIN (
    SELECT receiver, user_id, MAX(created_at) AS last_sent
        FROM sms
        WHERE user_id = ?
        GROUP BY receiver, user_id
    ) temp
ON S.receiver = temp.receiver
AND S.user_id = temp.user_id
AND S.created_at = temp.last_sent
LEFT OUTER JOIN indexes I ON S.receiver = I.phone_number WHERE I.user_id = ? 
ORDER BY temp.last_sent DESC

此 SQL 请求有效。我通过接收者名称获取用户发送给它的最后一条短信。但我只收到接收器出现在索引表中的短信。所有发送给未在此数据库中保存电话号码的接收者的 SMS 都不会显示。

我知道我的LEFT OUTER JOIN indexes. 但

那么如何获取接收者发送的最后一条短信，按 last_sent 排序，电话号码是否保存在索引中？

谢谢。

4

1 回答 1

2

将 WHERE 子句移动到 LEFT OUTER JOIN 的 ON 子句中

SELECT S.receiver, S.message, I.name, temp.last_sent, I.id
FROM sms S
INNER JOIN (
    SELECT receiver, user_id, MAX(created_at) AS last_sent
        FROM sms
        WHERE user_id = ?
        GROUP BY receiver, user_id
    ) temp
ON S.receiver = temp.receiver
AND S.user_id = temp.user_id
AND S.created_at = temp.last_sent
LEFT OUTER JOIN indexes I ON S.receiver = I.phone_number 
AND I.user_id = ? 
ORDER BY temp.last_sent DESC
于 2013-06-28T08:22:18.850 回答