sql - 将行值转换为 SQL Server 中的列 (PIVOT)

Question

我在 SQL Server 中有一个名为 test 的表，有 3 列

|  ITEM | ATTRIBUTE | VALUE |
-----------------------------
| item1 |   Quality |     A |
| item1 |     color |   Red |
| item2 |   Quality |     B |
| item2 |     color | Black |

我想要这样的输出:

|  ITEM | QUALITY | COLOR |
---------------------------
| item1 |       A |   Red |
| item2 |       B | Black |

如何在SQL Server中获得此信息。

Answer 1

试试这个:

SELECT *
FROM (SELECT Item, attribute, value FROM MyTable) AS t
PIVOT
(
  MAX(value)
  FOR attribute IN([Quality], [Color])
) AS p;

输出:

╔═══════╦═════════╦═══════╗
║ ITEM  ║ QUALITY ║ COLOR ║
╠═══════╬═════════╬═══════╣
║ item1 ║ A       ║ Red   ║
║ item2 ║ B       ║ Black ║
╚═══════╩═════════╩═══════╝

见 this SQLFiddle

如果您不知道 attribute 的具体值，也可以使用此动态查询:

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

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


set @query = 'SELECT Item,' + @cols + ' 
             from 
             (
                Select Item, attribute , value
                from MyTable
             ) dta
             pivot 
             (
                MAX(Value)
                for attribute in (' + @cols + ')
             ) pvt '

execute(@query);

见 this SQLFiddle