当记录非常庞大时，Mysql列作为行（透视表）的查询速度非常慢

我正试图编写一个查询来创建一个数据“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'

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）：

我必须查询以生成上述结果。这是我的问题

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

选择'CategoryId`，
最大值（如果（c.`ProcessedOn`='2011-04-20'，c.`PercentChange`，NULL））为'2011-04-20'，
最大值（如果（c.`ProcessedOn`='2011-04-21'，c.`PercentChange`，NULL））为'2011-04-21'，
最大值（如果（c.`ProcessedOn`='2011-04-22'，c.`PercentChange`，NULL））为'2011-04-22'，
最大值（如果（c.`ProcessedOn`='2011-04-23'，c.`PercentChange`，NULL））为'2011-04-23'，
最大值（如果（c.`ProcessedOn`='2011-04-24'，c.`PercentChange`，NULL））为'2011-04-24'
摘自`类别` c
其中c.`ProcessedOn`>='2011-04-20'
和c.“加工过的”`
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    |
--------------------------------------------------------------------------------

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