需要帮助构建 MySQL Query答案

【问题标题】：Need help constructing MySQL Query需要帮助构建 MySQL Query
【发布时间】：2013-02-11 02:01:11
【问题描述】：

我的数据&表格如下：

+------+------------+-----------+--------------+------------+----------+-------------+
| sr   | thread_id  | thread_no | client_name  | date       | time     | status      |
+------+------------+-----------+--------------+------------+----------+-------------+
|  871 | 1281473902 |         0 | Demo Company | 2011-01-17 | 16:53:00 | Closed      |
| 1179 | 1269343346 |         0 | Demo Company | 2010-03-23 | 11:22:00 | Open        |
| 1180 | 1269343585 |         0 | Demo Company | 2010-03-23 | 11:26:00 | Closed      |
| 1181 | 1269343679 |         0 | Demo Company | 2010-03-23 | 11:27:00 | Open        |
| 1182 | 1269343835 |         0 | Demo Company | 2010-03-23 | 11:30:00 | Open        |
| 2392 | 1295285762 |         0 | Demo Company | 2011-01-17 | 17:35:00 | Closed      |
| 2393 | 1295286578 |         0 | Demo Company | 2011-01-18 | 08:01:00 | Open        |
| 2526 | 1299764352 |         0 | Demo Company | 2011-04-29 | 11:01:00 | Closed      |
| 8727 | 1299764352 |         1 | Demo Company | 2011-06-16 | 09:31:00 | Closed      |
| 8728 | 1299764352 |         2 | Demo Company | 2011-06-16 | 09:56:00 | Closed      |
| 8729 | 1299764352 |         3 | Demo Company | 2011-06-16 | 09:57:00 | Closed      |
| 8731 | 1308234742 |         0 | Demo Company | 2011-06-16 | 10:31:00 | Open        |
| 8734 | 1308236479 |         0 | Demo Company | 2011-06-16 | 11:00:00 | Open-Urgent |
| 8735 | 1308236519 |         0 | Demo Company | 2011-06-16 | 11:01:00 | On Hold     |
| 8736 | 1308236519 |         1 | Demo Company | 2011-06-16 | 11:02:00 | Closed      |
| 8740 | 1308242129 |         0 | Demo Company | 2011-06-16 | 12:34:00 | Closed      |
| 8796 | 1308242129 |         1 | Demo Company | 2011-06-24 | 06:27:00 | Closed      |
| 8798 | 1308242129 |         2 | Demo Company | 2011-06-24 | 07:43:00 | Open        |
| 8799 | 1308242129 |         3 | Demo Company | 2011-06-24 | 07:44:00 | Open        |
+------+------------+-----------+--------------+------------+----------+-------------+

我需要选择具有 DISTINCT thread_id 并且该不同 thread_id 具有最高 thread_no 值的 ROWS

例如对于thread_id 1299764352，我需要选择sr=8729的行

我可以通过这个查询得出结论：

SELECT sr, thread_id, max(thread_no) as thread_no, client_name, date, time, status 
    FROM table 
    group by thread_id 
    order by sr

但是这个查询给了我 thread_no=0 的行，而不是 thread_no 值最高的行

希望我能解释清楚。

请帮忙。

谢谢呸

【问题讨论】：

标签： mysql sql

【解决方案1】：

我猜你需要以下查询：

SELECT * FROM table AS a
WHERE NOT EXISTS (
SELECT * FROM table AS b 
WHERE b.thread_id = a.thread_id AND b.thread_no > a.thread_no )

【讨论】：

您可以通过选择代码并单击{} 按钮使您的代码看起来像代码。
那么您不会这么好心批准我的回答吗？ :)

【解决方案2】：

试试：

SELECT * FROM table 
GROUP BY thread_id 
ORDER BY MAX(thread_no) DESC, sr ASC

【讨论】：

@Grigor Gevorgyan 提供的解决方案非常完美。谢谢@Grigor Gevorgyan
@vai：无论哪种解决方案都适合您。首先检查它是否有效，然后检查速度差异。 ;)

【解决方案3】：

我猜您正在寻找分析函数“partition by”。请参阅this 文章。

【讨论】：

【解决方案4】：

SELECT m.* 
FROM myTable AS m
  JOIN
    ( SELECT thread_id
           , MAX(thread_no) AS max_no
      FROM myTable
      GROUP BY thread_id
    ) AS grp
    ON m.thread_id = grp.thread_id
    AND m.thread_no = grp.max_no

或像这样（感谢Quassnoi）：

SELECT m.* 
FROM 
    ( SELECT DISTINCT thread_id
      FROM myTable
    ) AS md
  JOIN myTable AS m
    ON m.sr =
      ( SELECT mi.sr
        FROM myTable mi
        WHERE mi.thread_id = md.thread_id
        ORDER BY mi.thread_no DESC
        LIMIT 1
      )

【讨论】：