简化 SQL SELECT 语句？

Question

我有一个查询，它会提取 36 个月的滚动单位销售历史记录。它按原样工作，但我想知道是否有办法让它变得不那么冗长和繁琐。

查询有两部分 - 标题和数据。

这是我的标题：

SELECT  
DATEADD(m, -36, GETDATE()-day(GETDATE()-1)) AS  "MM36"
, DATEADD(m, -35, GETDATE()-day(GETDATE()-1)) AS  "MM35"
, DATEADD(m, -34, GETDATE()-day(GETDATE()-1)) AS  "MM34"

截至今天，这是 2011 年 9 月 - 11 月。它继续...

, DATEADD(m, -03, GETDATE()-day(GETDATE()-1)) AS  "MM03"
, DATEADD(m, -02, GETDATE()-day(GETDATE()-1)) AS  "MM02"
, DATEADD(m, -01, GETDATE()-day(GETDATE()-1)) AS  "MM01"

2014 年 6 月 - 8 月。36 行代码。

拉取销量数据的语句如下：

, SUM (CASE WHEN "SalesTable"."SalesDate" BETWEEN DATEADD(m, -36, GETDATE()-day(GETDATE()-1)) AND DATEADD(m, -35, GETDATE()-day(GETDATE()-1))-1 THEN "SalesTable"."SalesQty" - "SalesTable"."ReturnsQty"  ELSE NULL END) AS "NetQty36"
 , SUM (CASE WHEN "SalesTable"."SalesDate" BETWEEN DATEADD(m, -35, GETDATE()-day(GETDATE()-1)) AND DATEADD(m, -34, GETDATE()-day(GETDATE()-1))-1 THEN "SalesTable"."SalesQty" - "SalesTable"."ReturnsQty" ELSE NULL END) AS "NetQty35"
 , SUM (CASE WHEN "SalesTable"."SalesDate" BETWEEN DATEADD(m, -34, GETDATE()-day(GETDATE()-1)) AND DATEADD(m, -33, GETDATE()-day(GETDATE()-1))-1 THEN "SalesTable"."SalesQty" - "SalesTable"."ReturnsQty" ELSE NULL END) AS "NetQty34"

截至今天，这是 2011 年 9 月 - 11 月。它继续...

 , SUM (CASE WHEN "SalesTable"."SalesDate" BETWEEN DATEADD(m, -03, GETDATE()-day(GETDATE()-1)) AND DATEADD(m, -02, GETDATE()-day(GETDATE()-1))-1 THEN "SalesTable"."SalesQty" - "SalesTable"."ReturnsQty" ELSE NULL END) AS "NetQty03"
 , SUM (CASE WHEN "SalesTable"."SalesDate" BETWEEN DATEADD(m, -02, GETDATE()-day(GETDATE()-1)) AND DATEADD(m, -01, GETDATE()-day(GETDATE()-1))-1 THEN "SalesTable"."SalesQty" - "SalesTable"."ReturnsQty" ELSE NULL END) AS "NetQty02"
 , SUM (CASE WHEN "SalesTable"."SalesDate" BETWEEN DATEADD(m, -01, GETDATE()-day(GETDATE()-1)) AND DATEADD(m, -00, GETDATE()-day(GETDATE()-1))-1 THEN "SalesTable"."SalesQty" - "SalesTable"."ReturnsQty" ELSE NULL END) AS "NetQty01"

2014 年 6 月 - 8 月。

在完成这份报告之前，我还有很多东西要补充，所以我希望尽可能保持整洁。

谢谢，

编辑

下面的示例表明，通过上面的代码，我能够得到我想要的（没有代表发布图像，所以我必须做一个链接）。它还表明，使用数据透视表我缺少我的项目编号和滚动月份。我如何添加这两个东西？

Example

我尝试如下删除“ItemTable”.“ItemNum”字段，但它没有显示在我的 Crystal Report 中。在我尝试将它放在其他任何地方时，都会出现“无法绑定”错误。

select 
[0] MM00
, [1] MM01
, [2] MM02
, ...
from (
select 
  "ItemTable"."ItemNum",DateDiff(m, "SalesTable"."SalesDate", GetDate()) months_ago
, "SalesTable"."SalesQty" - "SalesTable"."ReturnsQty" NetQty
from your_table
) as source
pivot 
(
 sum(NetQty) For months_ago in ([0], [1], [2], [3], ...)
) as PivotTable

再次感谢。

Answer 1

Pivot table 的情况似乎已经成熟。

类似的东西

select 
    [0] MM00
  , [1] MM01
  , [2] MM02
  , ...
from (
  select 
      DateDiff(m, "SalesTable"."SalesDate", GetDate()) months_ago
    , "SalesTable"."SalesQty" - "SalesTable"."ReturnsQty" NetQty
  from your_table
) as source
pivot 
(
  sum(NetQty) For months_ago in ([0], [1], [2], [3], ...)
) as PivotTable

编辑

优化示例：包括项目编号相当简单；只需将其包含在 select 语句中即可。

select 
    "ItemTable"."ItemNum"
  , [0] MM00
  , [1] MM01
  , [2] MM02
  , ...
from (
  select
      "ItemTable"."ItemNum" 
    , DateDiff(m, "SalesTable"."SalesDate", GetDate()) months_ago
    , "SalesTable"."SalesQty" - "SalesTable"."ReturnsQty" NetQty
  from your_table
) as source
pivot 
(
  sum(NetQty) For months_ago in ([0], [1], [2], [3], ...)
) as PivotTable

为数据透视列设置动态名称相当困难。一般的想法是您必须将 SQL 构建为字符串并动态执行它。 Google 搜索会产生许多结果（例如a SQL Hints blog）。一些不完整的代码可以给你大致的想法。

SET @DynamicPivotQuery = 
 N'select 
    "ItemTable"."ItemNum"
  , [' + @Name1 + ']
  , [' + @Name2 + ']
  , [' + @NameN + ']
from (
  select
      "ItemTable"."ItemNum" 
      /* search MSDN for the best date formatting algorithm */
    , CONVERT_TO_STRING("SalesTable"."SalesDate") month 
    , "SalesTable"."SalesQty" - "SalesTable"."ReturnsQty" NetQty
  from your_table
) as source
pivot 
(
  sum(NetQty) For month in (
      [' + @Name1 + ']
    , [' + @Name2 + ']
    , [' + @NameN + ']
  )
) as PivotTable';

--Execute the Dynamic Pivot Query
EXEC sp_executesql @DynamicPivotQuery