sql - 数据透视表和连接列

Question

我有以下格式的数据库:

 ID    TYPE   SUBTYPE    COUNT   MONTH
 1      A      Z          1       7/1/2008
 1      A      Z          3       7/1/2008
 2      B      C          2       7/2/2008
 1      A      Z          3       7/2/2008

我可以使用 SQL 将其转换成这样吗:

ID    A_Z   B_C   MONTH
1     4     0     7/1/2008
2     0     2     7/2/2008
1     0     3     7/2/2008

因此，TYPE、SUBTYPE 被连接到新的列中，COUNT 在 ID 和MONTH 匹配。

如有任何提示，我们将不胜感激。这在 SQL 中可行还是我应该手动编程？

数据库是SQL Server 2005。

假设有 100 个 TYPES 和 SUBTYPES，那么“A”和“Z”不应该是硬编码的，而是动态生成的。

Answer 1

SQL Server 2005 提供了一个非常有用的 PIVOT 和 UNPIVOT 运算符，允许您使用 PIVOT 和一些代码生成/动态 SQL 使此代码免维护

/*
CREATE TABLE [dbo].[stackoverflow_159456](
    [ID] [int] NOT NULL,
    [TYPE] [char](1) NOT NULL,
    [SUBTYPE] [char](1) NOT NULL,
    [COUNT] [int] NOT NULL,
    [MONTH] [datetime] NOT NULL
) ON [PRIMARY]
*/

DECLARE @sql AS varchar(max)
DECLARE @pivot_list AS varchar(max) -- Leave NULL for COALESCE technique
DECLARE @select_list AS varchar(max) -- Leave NULL for COALESCE technique

SELECT @pivot_list = COALESCE(@pivot_list + ', ', '') + '[' + PIVOT_CODE + ']'
        ,@select_list = COALESCE(@select_list + ', ', '') + 'ISNULL([' + PIVOT_CODE + '], 0) AS [' + PIVOT_CODE + ']'
FROM (
    SELECT DISTINCT [TYPE] + '_' + SUBTYPE AS PIVOT_CODE
    FROM stackoverflow_159456
) AS PIVOT_CODES

SET @sql = '
;WITH p AS (
    SELECT ID, [MONTH], [TYPE] + ''_'' + SUBTYPE AS PIVOT_CODE, SUM([COUNT]) AS [COUNT]
    FROM stackoverflow_159456
    GROUP BY ID, [MONTH], [TYPE] + ''_'' + SUBTYPE
)
SELECT ID, [MONTH], ' + @select_list + '
FROM p
PIVOT (
    SUM([COUNT])
    FOR PIVOT_CODE IN (
        ' + @pivot_list + '
    )
) AS pvt
'

EXEC (@sql)