T-SQL 选择不同值的样本记录

Question

在 SQL Server 2008 中，我有表 Theory，其中包含列 Thesis 和 Class。

Thesis                   Class
<this is sample text>    1
<this is sample text>    2
<this is sample text>    2
<this is sample text>    3
<this is sample text>    3
<this is sample text>    1
<this is sample text>    3
<this is sample text>    1
<this is sample text>    1
<this is sample text>    2

我想编写将返回每个类的两条记录的选择语句。

非常感谢

Answer 1

;WITH T AS
(
SELECT Thesis, 
       Class, 
       ROW_NUMBER() OVER (PARTITION BY Class ORDER BY (SELECT 0) ) rn
FROM Theory 
)
SELECT Thesis, Class
FROM T 
WHERE rn <=2