我想知道其他人如何处理这种情况......以及如何将不要重复自己（DRY）原则应用于这种情况。
我发现自己经常 PIVOTing 或在 T-SQL 中编写 CASE 语句以将 Months 呈现为列。我通常有一些字段，其中包括 (1) 日期字段和 (2) 值字段。当我通过 ASPX 页面或 Reporting Services 将其呈现给用户时，我需要拥有最后最右边的 14 列才能具有这种模式：
[年],[一月],[二月],[三月],[四月],[五月],[六月],[七月],[八月],[九月],[十月],[十一月],[十二月] ]，[全部的]
其中 year 是 int 形式的年份，每个其他字段是该月的总和值字段（[Total] 除外，它是年份的总值字段）。
我想找到一种可重复使用的方法来处理这个问题。对所有建议开放 (T-SQL / ANSI SQL)
这并不完全是您要寻找的，但我已经做了很多重复的工作UNPIVOT，通常，我会使用某种标准化命名和大量使用 CTE 来编写代码：
WITH P AS (
SELECT Some Data
,[234] -- These are stats
,[235]
FROM Whatever
)
,FINAL_UNPIVOTED AS (
SELECT Some Data
,[STAT]
FROM P
UNPIVOT (
STAT FOR BASE IN ([234], [235])
) AS unpvt
WHERE STAT <> 0
)
SELECT Some Data
,CONVERT(int, FINAL_UNPIVOTED.[BASE]) AS [BASE]
,FINAL_UNPIVOTED.[STAT]
FROM FINAL_UNPIVOTED
您可以通过检查表或视图并使用如下代码生成代码：
DECLARE @sql_unpivot AS varchar(MAX)
SELECT @sql_unpivot = COALESCE(@sql_unpivot + ',', '') + COLUMN_NAME
FROM INFORMATION_SCHEMA.TABLES
WHERE TABLE_NAME = 'whatever'
并将代码模板化：
SET @template = '
WITH P AS (
SELECT Some Data
,{@sql_unpivot}
FROM Whatever
)
,FINAL_UNPIVOTED AS (
SELECT Some Data
,[STAT]
FROM P
UNPIVOT (
STAT FOR BASE IN ({@sql_unpivot})
) AS unpvt
WHERE STAT <> 0
)
SELECT Some Data
,CONVERT(int, FINAL_UNPIVOTED.[BASE]) AS [BASE]
,FINAL_UNPIVOTED.[STAT]
FROM FINAL_UNPIVOTED
'
SET @sql = REPLACE(@template, '{@sql_unpivot}', @sql_unpivot)
等等
当然，可以动态运行此代码或创建和 SP，您可以换出临时创建的视图或表，以便为内联的内容获取元数据。
请参阅有关表值函数和 OUTER APPLY 技术的评论。
已经很晚了，我可能在这里遗漏了一些明显的东西，但是每个月都有一行的 Months 表可以帮助你做到这一点吗？
/* I leave year and month separate so you can use "real" Months or Fiscal Months */
CREATE FUNCTION [dbo].[fn_MonthValueColumns]
(
@year int,
@month int,
@measure int
)
RETURNS TABLE
AS
RETURN
(
SELECT @year as [Year],
CASE WHEN @month = 1 THEN @measure ELSE 0 END AS [Jan],
CASE WHEN @month = 2 THEN @measure ELSE 0 END AS [Feb],
CASE WHEN @month = 3 THEN @measure ELSE 0 END AS [Mar],
CASE WHEN @month = 4 THEN @measure ELSE 0 END AS [Apr],
CASE WHEN @month = 5 THEN @measure ELSE 0 END AS [May],
CASE WHEN @month = 6 THEN @measure ELSE 0 END AS [Jun],
CASE WHEN @month = 7 THEN @measure ELSE 0 END AS [Jul],
CASE WHEN @month = 8 THEN @measure ELSE 0 END AS [Aug],
CASE WHEN @month = 9 THEN @measure ELSE 0 END AS [Sep],
CASE WHEN @month = 10 THEN @measure ELSE 0 END AS [Oct],
CASE WHEN @month = 11 THEN @measure ELSE 0 END AS [Nov],
CASE WHEN @month = 12 THEN @measure ELSE 0 END AS [Dec],
@measure AS [Total]
)
/*
use a group by after your own CROSS APPLY to roll-up SUMs for the last 13 fields.
this function and a CROSS APPLY against 100000 records ran in 3 seconds.
for what I am doing, I can live with that performance.
*/
使用视图怎么样？
如果您总是使用同一张表/一组表，则视图可能有意义。警告：当使用大表的一小部分时，请注意这样的视图。视图可能会阻止优化器完成它的工作。