Sql Server查询数据集行列互换

行换列：
--> 生成测试数据表: [tb]
IF OBJECT_ID('[tb]') IS NOT NULL
    DROP TABLE [tb]
GO
CREATE TABLE [tb] ([a] [int],[b] [int],[c] [int])
INSERT INTO [tb]
SELECT '3','9','5' UNION ALL
SELECT '5','2','7' UNION ALL
SELECT '6','3','8'
--SELECT * from [tb]
-->SQL查询如下:
select value maxnum from tb unpivot(value for type in(a,b,c)) b
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列换行：
待补充