1．假设学生—课程数据库关系模式如下： S（Sno，Sname，Sage，Ssex) C（Cno

2 select sname, 2014-Sage from S

3 select sname, sage from S where sage between 20 and 22

4 select * from S order by sdept asc, sage desc

5 select S.sno, sname from S, C, SC where S.sno=SC.sno and SC.cno=C.cno and Cname='数据库

SELECT Student.SName,Course.Cname,SC.Score

FROM SC

LEFT JOIN Student ON SC.SNo = Student.SNo

LEFT JOIN Course ON SC.CNo = Course.CNo

WHERE Student.SNo = '20080101'

2)

UPDATE Student SET SAge = SAge + 2

3.

INSERT INTO Student(SNo, SName, SAge, SDept) VALUES ('20080102', '李汉', '20', 'soft')