在SQL Server中使用数据透视缩小和分组列

Question

我有一个SQL表：

DECLARE @team TABLE (Department VARCHAR(20),TeamMember1 VARCHAR(50),TeamMember2 VARCHAR(50),TeamMember3 VARCHAR(50))

INSERT INTO @team VALUES('CRM','Tom', 'Harry', 'Rodger')
INSERT INTO @team VALUES('ERP','Boby', 'Simha', 'Wonder')
INSERT INTO @team VALUES('HR','Jack', 'John', 'Jim')

SELECT t.* FROM @team t

该表的输出应为

我的预期输出应为

我提到了许多教程，但找不到解决方案。 因此，请为我提供帮助...这是一个临时表，我需要在主项目中实现相同的逻辑。

Answer 1

首先，您应该知道将团队成员存储在单独的列中是错误的数据格式。 您想要的结果是更好的格式。

如果要学习SQL，一个简单的解决方案是UNION ALL ：

select Department, TeamMember1 as TeamMember from @team union all
select Department, TeamMember2 as TeamMember from @team union all
select Department, TeamMember3 as TeamMember from @team;

但是，在某些情况下，其他方法会更有效。 我倾向于使用：

select t.Department, v.TeamMember
from @team t outer apply
     (values (TeamMember1), (TeamMember2), (TeamMember3)) v(TeamMember);

Answer 2

SELECT t.*
FROM @team
CROSS APPLY (
    VALUES ('TeamMember1', TeamMember1)
         , ('TeamMember2', TeamMember2)
         , ('TeamMember3', TeamMember3)
) t(TeamName, TeamMember)