如何将多行数据合并为一？

Question

我正在使用SQL Server2008。我具有下表中的数据：

Team    Email              Groups
------- ------------------ ------
|Team1|-|[e-mail]|-|A|
|Team1|-|[e-mail]|-|B|
|Team1|-|[e-mail]|-|C|
|Team2|-|[e-mail]|-|A|
|Team2|-|[e-mail]|-|B|
|Team2|-|[e-mail]|-|C|

我想以这种格式获取数据：

Team    A                  B                  C
------- ------------------ ------------------ ------------------
|Team1|-|[e-mail]|-|[e-mail]|-|[e-mail]|
|Team2|-|[e-mail]|-|[e-mail]|-|[e-mail]|

我怎样才能做到这一点？

Answer 1

使用PIVOT您可以执行以下操作

With SampleData AS 
(
SELECT 'Team1' as Team , '[e-mail]' as email, 'A' as Groups
UNION SELECT 'Team1' as Team , '[e-mail]' as email, 'B' as Groups
UNION SELECT 'Team1' as Team , '[e-mail]' as email, 'C' as Groups
UNION SELECT 'Team2' as Team , '[e-mail]' as email, 'A' as Groups
UNION SELECT 'Team2' as Team , '[e-mail]' as email, 'B' as Groups
UNION SELECT 'Team2' as Team , '[e-mail]' as email, 'C' as Groups
)
SELECT Team, A, B,C FROM 
(SELECT * FROM SampleData) source
PIVOT
(MAX(email) FOR Groups IN ([A], [B], [C]) )as pvt

产生

Team  A                B                C
----- ---------------- ---------------- ----------------
Team1 [e-mail] [e-mail] [e-mail]
Team2 [e-mail] [e-mail] [e-mail]

查看有效的Data.SE示例

在不支持PIVOT的数据库中，您可以改为对表进行多次联接。尽管您可能还是想这样做，但是正如GBN所指出的那样，因为我们没有使用聚合。

With SampleData AS 
(
SELECT 'Team1' as Team , '[e-mail]' as email, 'A' as Groups
UNION SELECT 'Team1' as Team , '[e-mail]' as email, 'B' as Groups
UNION SELECT 'Team1' as Team , '[e-mail]' as email, 'C' as Groups
UNION SELECT 'Team2' as Team , '[e-mail]' as email, 'A' as Groups
UNION SELECT 'Team2' as Team , '[e-mail]' as email, 'B' as Groups
UNION SELECT 'Team2' as Team , '[e-mail]' as email, 'C' as Groups
)

SELECT 
    source.Team,
    A.email,
    B.email,
    C.email
FROM 
    (SELECT DISTINCT TEAM From SampleData) source
    LEFT JOIN SampleData A 
    ON source.Team = A.Team
     AND A.GROUPS = 'A'
    LEFT JOIN SampleData B 
    ON source.Team = B.Team
    AND B.GROUPS = 'B'
    LEFT JOIN SampleData C 
    ON source.Team = C.Team
    AND C.GROUPS = 'C'

查看有效的Data.SE示例