mysql ³£ÓþÙÀý

drop table student;
create table student
(sno   int   not null unique,
 sname varchar(8) not null,
 ssex  char(2)    not null,
 sage int ,
 sdept varchar(20));
 
 select * from student;
 alter table student drop unique(sno);
 alter table student modify sno primary key;
 alter table student add constraints con_s check(ssex in('F', 'M'));
 
 insert into  student values ('0001', 'zhangwen', 'F', 24, 'math');
 insert into  student values ('0201', 'zhangzi', 'F', 24, 'jsj');
 insert into  student values ('0002', 'wangjing', 'M', 22, 'math');
 insert into  student values ('0301', 'lilu', 'M', 23, 'wuli');
 insert into  student values ('0003', 'wujun', 'M', 24, 'math');
 insert into  student values ('0202', 'wangli', 'F', 23, 'jsj');
 insert into  student values ('0203', 'jiangmin', 'M', 23, 'jsj');
 insert into  student values ('0302', 'lixiang', 'F', 23, 'wuli');
 insert into  student values ('0303', 'jinmin', 'F', 24, 'wuli');
 insert into  student values ('0304', 'jinmin', 'F', null, 'wuli');
 insert into  student values ('0204', 'jinmin', 'F', 22, '');
 delete from student where sno = '0204';
 update student set sname = 'luyong' where sno = '0304';
 insert into student values('0004','meinv','M',22,'math');
 insert into student values('0006','beauty','M',21,'math');
 ----------------------------------------------
 drop table course;
 create table course(cno int primary key,
                     cname varchar2(10) not null,
                     ccredite float(2));