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

1 select * from S
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='数携族据辩游弊磨数库