设有学生表S,课程表C及学生选课表S
C: S (Sno,Sname,Sdept,Sage,Ssex); C (Cno,Cname,Credit,Cpno); SC(Sno, Cno,Grade) 其中,各属性列的含义如下: Sno—学号,Sname—姓名,Sdept—系别,Sage—年龄,Ssex—性别 Cno—课程号,Cname-课程名,Credit—学分,Cpno—先行课 Grade—成绩。定义 :选课表(学号,课程号,成绩),定义学号和课程号为主键,且学号为参照学生表的外键,课程号为参照课程表的外键。其实现SQL语句是( )
选项:
A:create table SC (Sno char(12), Cno char(12), Grade int, primary key(Sno,Cno), foreign key(Sno) references S(Sno), foreign key(Cno) references C(Cno), );
B:alter table S alter column Sname char(30);
C:select Sno,Cno,Grade from SC Where (Cno=’C3’or Cno=’C4’) and Grade>=70;
D:insert into SC values(‘200215121’,’8’,78);
发布时间:2024-06-22 10:58:30