摘要： create table student(sno char(9) primary key,sname char(20) unique,ssex char(2),sage smallint,sdept char(20));create table course(cno char(4) primary key,cname char(40),cpno char(4),ccredit smallint,foreign key(cpno) references course(cno));create table sc(sno char(9),cno char(4),grade smallint,prim 阅读全文