基于单列数据的带有动态标题的MySQL数据透视表

问题描述

| 我正在尝试编写查询以创建数据的“表”，如下所示：

SELECT cs.`category_id`,cs.`ProcessDate`,cs.`PercentChange`
  FROM `Category_Statistics` cs
 WHERE cs.`ProcessDate` >= \'2011-05-10\'
   AND cs.`ProcessDate` <= \'2011-05-14\'

这将返回类似：

CategoryId  |  ProcessDate  | PercentChange
-------------------------------------------
category_4  |  2011-05-10   |      10
category_4  |  2011-05-11   |      18
category_4  |  2011-05012   |      12
...
category_7  |  2011-05-10   |      21
category_7  |  2011-05-11   |      7
...
category_12 |  2011-05-10   |      7
category_12 |  2011-05-11   |      15

现在，我希望结果是这样的（来自MySQL查询，而不是由应用程序操纵）：

CategoryId    | 2011-05-10 | 2011-05-11 | 2011-05-12 | 2011-05-13 | 2011-05-14 |
--------------------------------------------------------------------------------
category_4    |     10     |     18     |     12     |      9     |      14    |
category_7    |     21     |      7     |     16     |      14    |      13    |
categeory_12  |      7     |     15     |     11     |      19    |       8    |
--------------------------------------------------------------------------------

有两个注意事项： 日期范围可以增加或缩小 （取决于查询） 在某些情况下，PercentChange可能为null 案例（让我们说category_7 / 2011-05-12可能没有设置值） 所以最终我不太确定如何构建查询的选择部分以反映动态的列数（我知道它与CONCAT有关）。 编辑->部分工作代码->

SELECT `CategoryId`,MAX(IF(c.`ProcessedOn` = \'2011-04-20\',c.`PercentChange`,NULL)) AS \'2011-04-20\',MAX(IF(c.`ProcessedOn` = \'2011-04-21\',NULL)) AS \'2011-04-21\',MAX(IF(c.`ProcessedOn` = \'2011-04-22\',NULL)) AS \'2011-04-22\',MAX(IF(c.`ProcessedOn` = \'2011-04-23\',NULL)) AS \'2011-04-23\',MAX(IF(c.`ProcessedOn` = \'2011-04-24\',NULL)) AS \'2011-04-24\'
  FROM `Category_Gravity` c
 WHERE c.`ProcessedOn` >= \'2011-04-20\'
   AND c.`ProcessedOn` <= \'2011-04-24\'
 GROUP BY `CategoryId`

我现在要做的是将

MAX(IF(c.`ProcessedOn` = \'2011-04-20\',

变成更动态的内容（因为我的日期范围会改变）     

解决方法

        看看这个类似的线程，我在其中写了一个sp以完成任务 将两个表（具有1-M关系）联接在一起，其中第二个表需要“展平”到一行 编辑。更新的答案

create table `pivot` (
  `id` int(11) not null auto_increment,`categoryid` int(11) default null,`processdate` date default null,`percentchange` int(11) default null,primary key (`id`)
) engine=myisam auto_increment=9 default charset=latin1;

/*Data for the table `pivot` */

insert  into `pivot`(`id`,`categoryid`,`processdate`,`percentchange`) values (1,4,\'2011-05-10\',1);
insert  into `pivot`(`id`,`percentchange`) values (2,\'2011-05-11\',22);
insert  into `pivot`(`id`,`percentchange`) values (3,\'2011-05-12\',3);
insert  into `pivot`(`id`,`percentchange`) values (4,7,4);
insert  into `pivot`(`id`,`percentchange`) values (5,5);
insert  into `pivot`(`id`,`percentchange`) values (6,12,6);
insert  into `pivot`(`id`,`percentchange`) values (7,7);
insert  into `pivot`(`id`,`percentchange`) values (8,\'2011-05-13\',12);



delimiter //
drop procedure if exists dynamic_view2//
create procedure dynamic_view2(in sdate date,in edate date)
begin
declare finish int default 0;
declare cdate date;
declare str varchar(10000) default \"select categoryid,\";
declare curs cursor for select processdate from pivot where processdate between sdate and edate group by processdate;
declare continue handler for not found set finish = 1;
open curs;
my_loop:loop
fetch curs into cdate;
if finish = 1 then
leave my_loop;
end if;
set str = concat(str,\"max(case when processdate = \'\",cdate,\"\' then percentchange else null end) as `\",\"`,\");
end loop;
close curs;
set str = substr(str,1,char_length(str)-1);
set @str = concat(str,\" from pivot
            group by categoryid\");

prepare stmt from @str;
execute stmt;
deallocate prepare stmt;
end;//
delimiter ;


mysql> call dynamic_view2(\'2011-05-10\',\'2011-05-13\');
+------------+------------+------------+------------+------------+
| categoryid | 2011-05-10 | 2011-05-11 | 2011-05-12 | 2011-05-13 |
+------------+------------+------------+------------+------------+
|          4 |          1 |         22 |          3 |         12 |
|          7 |          4 |          5 |       NULL |       NULL |
|         12 |          6 |       NULL |          7 |       NULL |
+------------+------------+------------+------------+------------+
3 rows in set (0.00 sec)