相关疑难解决方法(0)

我试图搜索帖子,但我只找到了SQL Server/Access的解决方案.我需要一个MySQL(5.X)的解决方案.

我有一个表(称为历史)有3列:hostid,itemname,itemvalue.
如果我执行select(select * from history),它将返回

   +--------+----------+-----------+
   | hostid | itemname | itemvalue |
   +--------+----------+-----------+
   |   1    |    A     |    10     |
   +--------+----------+-----------+
   |   1    |    B     |     3     |
   +--------+----------+-----------+
   |   2    |    A     |     9     |
   +--------+----------+-----------+
   |   2    |    c     |    40     |
   +--------+----------+-----------+

如何查询数据库以返回类似的内容

   +--------+------+-----+-----+
   | hostid |   A  |  B  |  C  |
   +--------+------+-----+-----+
   |   1    |  10  |  3  |  0  |
   +--------+------+-----+-----+
   |   2    |   9  |  0  |  40 …

如何在MySQL存储过程中构建和使用动态sql？

我正在尝试编写一个查询来创建数据的"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'

哪个会返回类似的东西:

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,不受应用程序操纵):

CategoryId    | 2011-05-10 | 2011-05-11 | 2011-05-12 | 2011-05-13 | 2011-05-14 |
--------------------------------------------------------------------------------
category_4    |     10     |     18     | …