Question

我有以下MySQL表设置：SQL Fiddle SQL Fiddle #2 - 我想要实现的是为每个单独的号码选择最新的消息。 From和To始终是这样或那样的，取决于消息的方向。此表中可能列出了多个数字。

感谢。

messages_outgoing

+----+----------------+----------------+--------------------------+-----------+---------------------+
| ID |             TO |           FROM |                     BODY | SMSSTATUS |                DATE |
+----+----------------+----------------+--------------------------+-----------+---------------------+
|  1 | +4407790000000 | +4407790000001 |         Outgoing Message |   pending | 2014-07-21 17:10:00 |
|  2 | +4407790000000 | +4407790000001 | Another outgoing message |   pending | 2014-07-21 17:20:00 |
|  3 | +4407790000000 | +4407790000001 |       Final message sent |   pending | 2014-07-21 17:30:00 |
|  4 | +4407790000003 | +4407790000001 |         Outgoing Message |   pending | 2014-07-21 17:30:00 |
|  5 | +4407790000004 | +4407790000001 |      Another message out |   pending | 2014-07-21 17:30:00 |
|  6 | +4407790000005 | +4407790000001 |      Information Message |   pending | 2014-07-21 17:40:00 |
+----+----------------+----------------+--------------------------+-----------+---------------------+

messages_incoming

+----+----------------+----------------+--------------------+---------------------------------+
| ID |             TO |           FROM |               BODY | SMSSTATUS |                DATE |
+----+----------------+----------------+--------------------+---------------------------------+
|  1 | +4407790000001 | +4407790000000 |  Replying to first |  received | 2014-07-21 17:15:00 |
|  2 | +4407790000001 | +4407790000000 | Replying to second |  received | 2014-07-21 17:25:00 |
|  3 | +4407790000001 | +4407790000005 |       OK, Received |  received | 2014-07-21 17:45:00 |
+----+----------------+----------------+--------------------+-----------+---------------------+

最终结果

+----+----------------+----------------+--------------------------+-----------+---------------------+----------+
| id | To             | From           | Body                     | SmsStatus | date                | source   | 
+----+----------------+----------------+--------------------------+-----------+---------------------+----------+
|  3 | +4407790000000 | +4407790000001 | Final message sent       | pending   | 2014-07-21 17:30:00 | outgoing |
|  4 | +4407790000003 | +4407790000001 | Outgoing Message         | pending   | 2014-07-21 17:30:00 | outgoing |
|  5 | +4407790000004 | +4407790000001 | Another message out      | pending   | 2014-07-21 17:30:00 | outgoing |
|  3 | +4407790000001 | +4407790000005 | OK, Received             | received  | 2014-07-21 17:45:00 | incoming |
+----+----------------+----------------+--------------------------+-----------+---------------------+----------+

+4407790000000与+4407790000001之间的对话 - 最新消息为“发送最终消息”

+4407790000003与+4407790000001之间的对话 - 最新消息为“外发留言”

+4407790000004和+4407790000001之间的对话 - 最新消息将是“另一条消息”

+4407790000005和+4407790000001之间的对话 - 最新消息为“OK，Received”

可能的解决方案

我提出了以下SQL查询。老实说，我认为这是一个非常糟糕的查询，它实际上是有效的并且返回我正在追求的内容。

SELECT `SmsStatus` , `Body` , `all_messages`.`Number` , `all_messages`.`date`
FROM (
    SELECT `SmsStatus` , `Body` , `To` as `Number` , `date` FROM `messages_outgoing`
    UNION
    SELECT `SmsStatus` , `Body` , `From` as `Number` , `date` FROM `messages_incoming`
) AS `messages`
INNER JOIN
(
    SELECT `messages`.`Number` , MAX(`date`) as `date`
    FROM (
        SELECT `SmsStatus` , `Body` , `To` as `Number` , `date` FROM `messages_outgoing`
        UNION
        SELECT `SmsStatus` , `Body` , `From` as `Number` , `date` FROM `messages_incoming`
    ) AS `messages` GROUP BY `Number`
) AS `all_messages`
ON `all_messages`.`Number` = `messages`.`Number` AND `all_messages`.`date` = `messages`.`date`

结果

+-----------+---------------------+----------------+---------------------+
| SMSSTATUS |                BODY |         NUMBER |                DATE |
+-----------+---------------------+----------------+---------------------+
|   pending |  Final message sent | +4407790000000 | 2014-07-21 17:30:00 |
|   pending |    Outgoing Message | +4407790000003 | 2014-07-21 17:30:00 |
|   pending | Another message out | +4407790000004 | 2014-07-21 17:30:00 |
|  received |        OK, Received | +4407790000005 | 2014-07-21 17:45:00 |
+-----------+---------------------+----------------+---------------------+

SQL Fiddle - Above Results

Answer 1

所以，鉴于这个中间结果，期望的结果集应该是什么样的？

SELECT *,'outgoing' source FROM messages_outgoing
UNION
SELECT *,'incoming' FROM messages_incoming;
+----+----------------+----------------+--------------------------+-----------+---------------------+----------+
| id | To             | From           | Body                     | SmsStatus | date                | source   | 
+----+----------------+----------------+--------------------------+-----------+---------------------+----------+
|  1 | +4407790000000 | +4407790000001 | Outgoing Message         | pending   | 2014-07-21 17:10:00 | outgoing |
|  2 | +4407790000000 | +4407790000001 | Another outgoing message | pending   | 2014-07-21 17:20:00 | outgoing |
|  3 | +4407790000000 | +4407790000001 | Final message sent       | pending   | 2014-07-21 17:30:00 | outgoing |
|  1 | +4407790000001 | +4407790000000 | Replying to first        | received  | 2014-07-21 17:15:00 | incoming |
|  2 | +4407790000001 | +4407790000000 | Replying to second       | received  | 2014-07-21 17:25:00 | incoming |
+----+----------------+----------------+--------------------------+-----------+---------------------+----------+

MySQL从多个表中选择最近的消息

1 个答案: