找到最後一個連續的行

Question

我需要一些幫助來查詢。

我有這個簡單的表：

CREATE TABLE `consecutiv` (
    `id` int(11) NOT NULL auto_increment, 
    `readVal` int(11) default NULL, 
    PRIMARY KEY (`id`) 
) ENGINE=MyISAM AUTO_INCREMENT=16 DEFAULT CHARSET=latin1; 


insert into `consecutiv`(`id`,`readVal`) values (1,2),(2,2),(3,2),(5,3),(6,3),(7,3),(8,3),(9,4),(10,5),(11,6),(12,6),(13,2),(14,2),(15,6); 

是這樣的：

id readVal 
    1 2 
    2 2 
    3 2 
    5 3 
    6 3 
    7 3 
    8 3 
    9 4 
    10 5 
    11 6 
    12 6 
    13 2 
    14 2 
    15 6 

我想對於一個給定readVal最後連續行：

在上面的例子將是：

id：3 for readVal = 2

ID：8 readVal = 3

... 

我試圖與此查詢：

SELECT consecutiv.id, consecutiv.readVal, c.id, c.readVal FROM consecutiv 
JOIN consecutiv c ON consecutiv.id = c.id-1 
WHERE consecutiv.readVal!=c.readVal ORDER BY consecutiv.id ASC 

而且只要沒有缺少ID系列中的它的工作原理。在上面的示例中，缺少4號，查詢不會返回預期的結果。

謝謝！

Answer 1

SELECT a.id, a.readVal 
FROM consecutiv a 
WHERE a.readVal != 
    (SELECT b.readVal 
    FROM consecutiv b 
    WHERE b.id > a.id 
    ORDER BY id ASC 
    LIMIT 1) 
ORDER BY a.id; 

回報：

id | readval 
----+--------- 
    3 |  2 
    8 |  3 
    9 |  4 
10 |  5 
12 |  6 
14 |  2 

的情況下的最後一行還需要：

SELECT c.id, c.readVal, c.nextReadVal 
FROM 
    (SELECT 
    a.id, a.readVal, 
    (SELECT b.readVal 
     FROM consecutiv b 
     WHERE b.id > a.id 
     ORDER BY id ASC 
     LIMIT 1) AS nextReadVal 
    FROM consecutiv a) AS c 
WHERE readVal != nextReadVal OR nextReadVal IS NULL 
ORDER BY c.id; 

回報：

id | readval | nextreadval 
----+---------+------------- 
    3 |  2 |   3 
    8 |  3 |   4 
    9 |  4 |   5 
10 |  5 |   6 
12 |  6 |   2 
14 |  2 |   6 
15 |  6 |