需要基于其他字段将多个字段合并为一个字段的帮助

Question

我最近问了一个类似的问题，但不幸的是，请求的性质发生了变化。我已经看了这段代码一段时间了，但我的大脑是朋友，我想不出一种方法让它按需工作。

在SQL2005中工作，这将包含数百个这样的值。

提前感谢！

示例表

+----+-------------+---------------------+---------------------+
| ID |    CLASS    |  PARENT_ATTRIBUTE   |      ATTRIBUTE      |
+----+-------------+---------------------+---------------------+
|  1 | Genre       | A                   | Hip Hop             |
|  1 | Genre       | B                   | Pop                 |
|  1 | Instruments | Keyboards           | Synth               |
|  1 | Instruments | Keyboards           | Grand Piano         |
|  1 | Instruments | Drums               | Kit                 |
|  1 | Moods       | Positive/Optimistic | Uplifting/Inspiring |
|  1 | Moods       | Positive/Optimistic | Happy/Feel Good     |
|  1 | Moods       | Musical Feel        | Pulsing             |
+----+-------------+---------------------+---------------------+

期望输出

+----+----------------------------------------------------------------------------------------------------------+---------------------------------------------------------+
| ID | MOODS                                                                                                    | INSTRUMENTS                                             |
| 1  |Positive/Optimistic - Uplifting/Inspiring, Positive/Optimistic -  Happy/Feel Good, Musical Feel - Pulsing | Keyboards - Synth, Keyboards - Grand Piano, Drums - Kit |
+----+----------------------------------------------------------------------------------------------------------+---------------------------------------------------------+

Answer 1

在将类放入列时使用MAX和CASE的技巧：

SELECT ID,
MAX(CASE WHEN class = 'Instruments' THEN attribs END) as INSTRUMENTS,
MAX(CASE WHEN class = 'Moods' THEN attribs END) as MOODS,
MAX(CASE WHEN class = 'Genre' THEN attribs END) as GENRES
FROM (
    SELECT
    id, class, 
    STUFF ((
        SELECT ', ' + parent_attribute + ' - ' + attribute
        FROM   YourTable i
        WHERE  i.ID = o.ID AND i.CLASS = o.CLASS
        FOR XML PATH('') 
    ), 1, 2, '') AS attribs
    FROM (SELECT DISTINCT id, class FROM YourTable) o
) q
GROUP BY id
ORDER BY id;

或者，在SQL Server 2008或更高版本上使用PIVOT：

select ID, 
[Instruments] as INSTRUMENTS,
[Moods] as MOODS,
[Genre] as GENRES
from (
    SELECT id, class,
    STUFF ((
        SELECT ', ' + parent_attribute + ' - ' + attribute
        FROM   YourTable i
        WHERE  i.ID = o.ID AND i.CLASS = o.CLASS
        FOR XML PATH('')
    ), 1, 2, '') AS attribs
    FROM (select distinct id, class from YourTable) o
) q
PIVOT (MAX(attribs) FOR class IN ([Instruments], [Moods], [Genre])
) pvt
order by id;

Answer 2

也许使用PIVOT你可以得到这样的输出，但我真的不知道如何……

请查看此链接：https://technet.microsoft.com/library/ms177410(v=sql.105).aspx