MySQL：使用子选择计算本地化的MIN MAX

Question

我正在建立一个基于MySQL的规范化数据集，其中包含过去五次观测值的相对值。为此，我需要知道过去五个数据点的最大值和最小值。我正在研究一个子查询，其工作原理如下：

我需要获取表中前五个事件的MIN和MAX。虽然我的表格目前按照DESC顺序排列，但我不能依靠它维护该结构，因为对于特定的MY_ID，RECENT_DATE的后续更新将更改最近的5个以及更新MY_VALUE。

这是我工作的基础表。

MY_ID | RECENT_DATE | MY_VALUE 
    392, 2013-10-06 12:00:00, 18332 
    146, 2013-09-06 12:00:00, 5623 
    72, 2013-09-02 12:00:00, 23242 
    643, 2013-09-01 12:00:00, 15242 
    492, 2013-08-06 12:00:00, 15332 
    346, 2013-07-26 12:00:00, 17332 
    172, 2013-07-22 12:00:00, 14001 
    123, 2013-07-22 12:00:00, 13918 
    243, 2013-07-11 12:00:00, 23229 

最后我需要它看起来像。

MY_ID | RECENT_DATE | MY_VALUE | MAX_VALUE | MIN_VALUE 
    392, 2013-10-06 12:00:00, 18332, 23242, 5623 
    146, 2013-09-06 12:00:00, 5623, 23242, 5623 
    72, 2013-09-02 12:00:00, 23242, 23242, 14001 
    643, 2013-09-01 12:00:00, 15242, 17332, 13918 
    492, 2013-08-06 12:00:00, 15332, 23229, 13918 
    346, 2013-07-26 12:00:00, 17332, 23229, 13918 
    172, 2013-07-22 12:00:00, 14001, 23229, 13918 
    123, 2013-07-22 12:00:00, 13918, 23229, 13918 
    243, 2013-07-11 12:00:00, 23229, 23229, 23229 

所以这里有一个快速的样品台

CREATE TABLE IF NOT EXISTS dbo.baseTable 
(
    MY_ID BIGINT(20) UNSIGNED, 
    RECENT_DATE DATETIME, 
    MY_VALUE BIGINT(20), 
); 

INSERT INTO dbo.baseTable (MY_ID, RECENT_DATE, MY_VALUE) VALUES (392, '2013-10-06 12:00:00', 18332); 
INSERT INTO dbo.baseTable (MY_ID, RECENT_DATE, MY_VALUE) VALUES (146, '2013-09-06 12:00:00', 5623); 
INSERT INTO dbo.baseTable (MY_ID, RECENT_DATE, MY_VALUE) VALUES (72, '2013-09-02 12:00:00', 23242); 
INSERT INTO dbo.baseTable (MY_ID, RECENT_DATE, MY_VALUE) VALUES (643, '2013-09-01 12:00:00', 15242); 
INSERT INTO dbo.baseTable (MY_ID, RECENT_DATE, MY_VALUE) VALUES (492, '2013-08-06 12:00:00', 15332); 
INSERT INTO dbo.baseTable (MY_ID, RECENT_DATE, MY_VALUE) VALUES (346, '2013-07-26 12:00:00', 17332); 
INSERT INTO dbo.baseTable (MY_ID, RECENT_DATE, MY_VALUE) VALUES (172, '2013-07-22 12:00:00', 14001); 
INSERT INTO dbo.baseTable (MY_ID, RECENT_DATE, MY_VALUE) VALUES (123, '2013-07-22 12:00:00', 13918); 
INSERT INTO dbo.baseTable (MY_ID, RECENT_DATE, MY_VALUE) VALUES (243, '2013-07-11 12:00:00', 23229); 

现在，这里是我的屠宰查询尝试：

SELECT DISTINCT t1.MY_ID, 
     t1.RECENT_DATE, 
     t1.MY_VALUE, MAX(t2.MY_VALUE) AS MAX_MY_VALUE, MIN(t2.MY_VALUE) AS MIN_MY_VALUE 
FROM dbo.baseTable t1 
    INNER JOIN (
     SELECT t.MY_ID, t1.RECENT_DATE, t.MY_VALUE 
      FROM dbo.baseTable t 
      WHERE t.RECENT_DATE <= t1.RECENT_DATE 
      LIMIT 5) AS t2 ON t1.MY_ID = t2.MY_ID 
/* WHERE OMITTED */ 
ORDER BY t1.RECENT_DATE DESC 
; 

Answer 1

此查询应该返回你所需要的结果：

SELECT 
    ta.MY_ID, ta.MY_ID, ta.RECENT_DATE, ta.MY_VALUE, 
    MAX(tb.MY_VALUE), 
    MIN(tb.MY_VALUE) 
FROM (
    SELECT 
    t1.MY_ID, 
    t1.RECENT_DATE, 
    t1.MY_VALUE, 
    SUBSTRING_INDEX(GROUP_CONCAT(t2.MY_ID ORDER BY t2.RECENT_DATE DESC), ',', 5) as Last_5 
    FROM 
    baseTable t1 INNER JOIN baseTable t2 
    ON t1.recent_date >= t2.recent_date 
    GROUP BY 
    t1.my_id 
) ta INNER JOIN baseTable tb ON FIND_IN_SET(tb.MY_ID, Last_5) 
GROUP BY 
    ta.MY_ID 
ORDER BY 
    RECENT_DATE DESC 

这不是标准SQL并使用一些MySQL技巧。 请参阅小提琴here。