CREATE TABLE Student 
(
  ID INT IDENTITY(1,1) PRIMARY KEY,
  学号 VARCHAR(40),
  姓名 VARCHAR(40),
  成绩 FLOAT
)
INSERT INTO Student VALUES('20110301','张三',82)
INSERT INTO Student VALUES('20110302','李四',85)
INSERT INTO Student VALUES('20110303','王五',86)
INSERT INTO Student VALUES('20110304','马六',87)
INSERT INTO Student VALUES('20110305','钱七',82)
INSERT INTO Student VALUES('20110301','张三',85)
INSERT INTO Student VALUES('20110303','王五',85)

SELECT * FROM Student 

SELECT * FROM Student WHERE ID IN (SELECT MIN(ID) FROM Student GROUP BY 学号)
/*
ID          学号                                       姓名                                       成绩                                                    
----------- ---------------------------------------- ---------------------------------------- ----------------------------------------------------- 
1           20110301                                 张三                                       82.0
2           20110302                                 李四                                       85.0
3           20110303                                 王五                                       86.0
4           20110304                                 马六                                       87.0
5           20110305                                 钱七                                       82.0

（所影响的行数为 5 行）
--DELETE FROM Student WHERE ID NOT IN(SELECT MIN(ID) FROM Student GROUP BY 学号)//删掉重复的
*/

------解决方案--------------------
数据有点出入，纠正一下
SQL code

CREATE TABLE Student 
(
  ID INT IDENTITY(1,1) PRIMARY KEY,
  学号 VARCHAR(40),
  姓名 VARCHAR(40),
  成绩 FLOAT
)
INSERT INTO Student VALUES('20110301','张三',82)
INSERT INTO Student VALUES('20110302','李四',84)
INSERT INTO Student VALUES('20110303','王五',85)
INSERT INTO Student VALUES('20110304','马六',86)
INSERT INTO Student VALUES('20110305','钱七',87)
INSERT INTO Student VALUES('20110301','张三',82)
INSERT INTO Student VALUES('20110303','王五',85)

SELECT * FROM Student 

SELECT * FROM Student WHERE ID IN (SELECT MIN(ID) FROM Student GROUP BY 学号)

--DELETE FROM Student WHERE ID NOT IN(SELECT MIN(ID) FROM Student GROUP BY 学号)这个也行
/*
ID          学号                                       姓名                                       成绩                                                    
----------- ---------------------------------------- ---------------------------------------- ---------------------
1           20110301                                 张三                                       82.0
2           20110302                                 李四                                       84.0
3           20110303