sql server 过滤重复数据

--先建立一个测试表：
CREATE TABLE [test] (
[id] [int] IDENTITY (1, 1) NOT NULL ,
[a] [varchar] (50) COLLATE Chinese_PRC_CI_AS NULL ,
[b] [varchar] (50) COLLATE Chinese_PRC_CI_AS NULL ,
[c] [varchar] (50) COLLATE Chinese_PRC_CI_AS NULL
) ON [PRIMARY]
GO

INSERT INTO [MisDB].[dbo].[test]([a], [b], [c])VALUES('a','b','c')
INSERT INTO [MisDB].[dbo].[test]([a], [b], [c])VALUES('a','b','cc')
INSERT INTO [MisDB].[dbo].[test]([a], [b], [c])VALUES('aa','bb','c')
INSERT INTO [MisDB].[dbo].[test]([a], [b], [c])VALUES('aa','bb','cc')
INSERT INTO [MisDB].[dbo].[test]([a], [b], [c])VALUES('a','bb','ccc')

--查询语句
select id,a,b,c from test a where
id=(SELECT min(id) FROM test b where a.a =b.a and a.b=b.b) order by id
结果：
1 a b c
3 aa bb c
5 a bb ccc