create table student //创建一个学生表
(
sno char(9) primary key, //定义学号为主码,,
///////每个表可以有多个 UNIQUE 约束,但是每个表只能有一个 PRIMARY KEY 约束
sname char(20) unique, //用unique来约束学生姓名,名字不可以重复
ssex char(3),
sage smallint, //smallint的取值范围是-2^15 (-32,768) 到 2^15-1 (32,767)
sdept char(20)
);
select * from student; //显示学生表当前的状态
insert into student(sname,ssex,sno,sage,sdept) values('邓景','女','12306','21','CP');
insert into student(sname,ssex,sno,sage,sdept) values('李彬','男','12307','21','JX');
insert into student(sname,ssex,sno,sage,sdept) values('陈浩','女','12304','21','LY');
insert into student(sname,ssex,sno,sage,sdept) values('叶问','男','12305','21','WS');
insert into student(sname,ssex,sno,sage,sdept) values('郑和','男','12302','21','EL');
insert into student(sname,ssex,sno,sage,sdept) values('小泳','女','12308','21','YC');
rollback; //回滚的意思就是数据库里做修改后 ( update ,insert , delete)未commit 之前
// 使用rollback 可以恢复数据到修改之前。
commit; //提交
CREATE table Course //创建一个课程表
(
Cno char