数据库实验：SQL的数据更新

实验目的

(1) 掌握DBMS的数据查询功能
(2) 掌握SQL语言的数据更新功能

实验内容

(1) update 语句用于对表进行更新
(2) delete 语句用于对表进行删除
(3) insert 语句用于对表进行插入

实验要求

(1) 熟练掌握SQL的数据更新语句INSERT、UPDATE、DELETE
(2) 写出实验报告

实验步骤

认真阅读S_T.sql，理解其中插入和修改语句的作用和用法；执行S_T.sql，建立示例数据库S_T
对学生关系Student、课程关系Course和选修关系SC进行数据插入、修改和删除元组（记录）的更新操作

S_T.sql即下述代码
在前文中也出现过

create database S_T;
go
use S_T;  /*将S_T设为当前数据库*/
create table Student
     (Sno CHAR(9) PRIMARY KEY,
      Sname CHAR(20) UNIQUE,
      Ssex CHAR(2),
      Sage SMALLINT,
      Sdept CHAR(20)
      );
go
/*表Student的主码为Sno，属性列Sname取唯一值*/
create table Course
      (Cno CHAR(4) PRIMARY KEY,
       Cname CHAR(40),
       Cpno CHAR(4),
       Ccredit SMALLINT,
       FOREIGN KEY (Cpno) REFERENCES Course(Cno)
       );
go
/*表Course的主码为Cno，属性列Cpno(先修课)为外码，被参照表为Course，被参照列是Cno*/
create table SC
      (Sno CHAR(9),
       Cno CHAR(4),
       Grade SMALLINT,
       primary key (Sno, Cno),
       FOREIGN KEY (Sno) REFERENCES Student(Sno),
       FOREIGN KEY (Cno) REFERENCES Course(Cno)
       );
go
 /*表SC的主码为(Sno, Cno), Sno和Cno均为外码，被参照表分别为Student和Course，被参照列分别为Student.Sno和Course.Cno*/
insert into student values('200215121','李勇','男',20,'CS');
insert into student values('200215122','刘晨','女',19,'CS');
insert into student values('200215123','王敏','女',18,'MA');
insert into student values('200215125','张立','男',19,'IS');
go
/*为表Student添加数据*/
insert into course values('1', '数据库', NULL,4);
insert into course values('2', '数学',  NULL,2);
insert into course values('3', '信息系统', NULL,4);
insert into course values('4', '操作系统', NULL,3);
insert into course values('5', '数据结构', NULL,4);
insert into course values('6', '数据处理', NULL, 2);
insert into course values('7', 'PASCAL语言',  NULL,4);
go
update Course set Cpno = '5' where Cno = '1';
update Course set Cpno = '1' where Cno = '3';
update Course set Cpno = '6' where Cno = '4';
update Course set Cpno = '7' where Cno = '5';
update Course set Cpno = '6' where Cno = '7';
/*为表Course添加数据*/
go
insert into SC values('200215121', '1',92);
insert into SC values('200215121', '2',85);
insert into SC values('200215121', '3',88);
insert into SC values('200215122', '2',90);
insert into SC values('200215122', '3',80);
/*为表SC添加数据*/
go