Question

我有一个包含3列的表：ItemCode，Quantity和DocDate。我想以更“优雅”的方式创建以下报告：

SELECT T0.ItemCode, 
       (SELECT SUM(QUANTITY) FROM MyTable T1 WHERE YEAR(T0.DocDate) = 2011 AND T0.ItemCode = T1.ItemCode) AS '2011',
       (SELECT SUM(QUANTITY) FROM MyTable T1 WHERE YEAR(T0.DocDate) = 2012 AND T0.ItemCode = T1.ItemCode) AS '2012'
FROM MyTable T0
GROUP BY T0.ItemCode, YEAR(T0.DocDate)

我很确定有更好，更有效的方式来编写这个但我无法提出正确的语法。有什么想法吗？

Answer 1

你可以试试这个：

SELECT  T0.ItemCode, 
        SUM(CASE WHEN YEAR(T0.DocDate) = 2011 THEN QUANTITY ELSE 0 END) AS '2011',
        SUM(CASE WHEN YEAR(T0.DocDate) = 2012 THEN QUANTITY ELSE 0 END) AS '2012'
FROM    MyTable T0
GROUP BY 
        T0.ItemCode

Answer 2

此类数据转换称为PIVOT。有几种方法可以执行此操作。您可以使用PIVOT函数，也可以使用带有CASE语句的聚合函数：

Static Pivot版本：这是您将所有值硬编码到查询中的地方

select ItemCode, [2011], [2012]
from
(
  SELECT ItemCode,
    QUANTITY,
    YEAR(DocDate) Year
  FROM MyTable 
) src
pivot
(
  sum(quantity)
  for year in ([2011], [2012])
) piv

请参阅SQL Fiddle with Demo

汇总案例：

SELECT ItemCode, 
  SUM(CASE WHEN YEAR(DocDate) = 2011 THEN QUANTITY ELSE 0 END) AS '2011',
  SUM(CASE WHEN YEAR(DocDate) = 2012 THEN QUANTITY ELSE 0 END) AS '2012'
FROM    MyTable 
GROUP BY ItemCode;

请参阅SQL Fiddle with Demo

动态数据透视：以前的两个版本效果很好，您可以使用已知数量的year值进行转换，但是您有一个未知数，那么您可以使用动态sql：

DECLARE @cols AS NVARCHAR(MAX),
    @query  AS NVARCHAR(MAX)

select @cols = STUFF((SELECT distinct ',' + QUOTENAME(YEAR(DocDate)) 
                    from mytable
            FOR XML PATH(''), TYPE
            ).value('.', 'NVARCHAR(MAX)') 
        ,1,1,'')

set @query = 'SELECT itemcode, ' + @cols + ' from 
             (
                select itemcode, quantity, year(docdate) year
                from mytable
            ) x
            pivot 
            (
                sum(quantity)
                for year in (' + @cols + ')
            ) p '

execute(@query)

请参阅SQL Fiddle with Demo

所有三个版本都会产生相同的结果：

| ITEMCODE | 2011 | 2012 |
--------------------------
|        1 |  200 |   45 |
|        2 |   89 |    0 |
|        3 |    0 |    7 |

SQL汇总报告，寻找优雅的解决方案

2 个答案: