create or replace table student(
 sid     int(11) primary key not null,
 sname   char(25) not null,
 age     int(11) not null,
 sex     char(2) not null,
 department char(40) ,
 address  char(200) ,
 birthplace  varchar(256)
);

create or replace table sc(
  sid   int(11) not null,
  cid   int(11) not null,
  grade int(11) 
);

create or replace table course(
  cid    int(11) not null primary key default 4,
  cname  char(40),
  teacher  char(40)
);

#以下是插入课程表的数据
delete from course ;
insert into course values('8108001','math','sandy');
insert into course values('8108002','english','sherry');
insert into course values('8108003','computer','sandy');
insert into course values('8108004','web','sandy');
insert into course values('8108005','java','sandy');
insert into course values('8108006','C languge','sherry');
insert into course values('8108007','python','xiaozhu');
insert into course values('8108008','testing','xiaozhu');
insert into course values('8108009','linux','sherry');
insert into course values('8108010','shell','sherry');

#以下是插入成绩级表的数据

delete from sc;
insert into sc values('3108001','8108010','90');
insert into sc values('3108001','8108003','67');
insert into sc values('3108002','8108003','54');
insert into sc values('3108002','8108010','84');
insert into sc values('3108003','8108003','78');
insert into sc values('3108004','8108004','89');
insert into sc values('3108005','8108006','56');
insert into sc values('3108006','8108005','60');
insert into sc values('3108007','8108004','79');
insert into sc values('3108008','8108008','89');
insert into sc values('3108009','8108002','46');
insert into sc values('3108010','8108003','87');
insert into sc values('3108011','8108001','85');
insert into sc values('3108011','8108002','81');
insert into sc values('3108012','8108001','97');
insert into sc values('3108012','8108002','55');
insert into sc values('3108013','8108002','86');
insert into sc values('3108013','8108001','71');
insert into sc values('3108014','8108002','69');
insert into sc values('3108014','8108001','78');
insert into sc values('3108015','8108002','67');
insert into sc values('3108016','8108001','85');
insert into sc values('3108016','8108003','85');
insert into sc values('3108016','8108002','85');
insert into sc values('3108016','8108004','85');
insert into sc values('3108016','8108005','85');
insert into sc values('3108016','8108006','80');
insert into sc values('3108016','8108007','79');
insert into sc values('3108016','8108009','36');
insert into sc values('3108016','8108010','78');
insert into sc values('3108016','8108008','88');
insert into sc values('3108016','8108021','83');
insert into sc values('3108015','8108001','85');
insert into sc values('3108015','8108003','85');
insert into sc values('3108015','8108004','85');
insert into sc values('3108015','8108005','85');
insert into sc values('3108015','8108006','80');
insert into sc values('3108015','8108007','79');
insert into sc values('3108015','8108009','36');
insert into sc values('3108015','8108010','78');
insert into sc values('3108015','8108008','88');
insert into sc values('3108015','8108021','83');

#----end

#以下是插入学生信息数据

delete from student;
insert into student values('3108001','wang min',21,'f','computer-tec','zhongshan road','jiangsu');
insert into student values('3108002','jidu',20,'m','english','zhongshan road','fujian');
insert into student values('3108003','wangqing',19,'f','computer-tec','zhongshan road','jiangsu');
insert into student values('3108004','liuxin',23,'f','chinese','zhongshan road','shanghai');
insert into student values('3108005','ligu',22,'f','computer-tec','zhongshan road','jiangsu');
insert into student values('3108006','songjia',19,'m','english','zhongshan road','jiangsu');
insert into student values('3108007','huamao',20,'f','chinese','zhongshan road','shanghai');
insert into student values('3108008','zhujiao',21,'f','english','zhongshan road','jiangsu');
insert into student values('3108009','wuyi',23,'m','computer-tec','zhongshan road','jiangsu');
insert into student values('3108010','jilian',18,'f','chinese','zhongshan road','hunan');
insert into student values('3108011','linbiao',22,'m','computer-tec','zhongshan road','jiangsu');
insert into student values('3108012','maoguai',21,'m','english','zhongshan road','fujian');
insert into student values('3108013','rongqi',23,'m','computer-tec','zhongshan road','jiangsu');
insert into student values('3108014','sangzi',20,'f','chinese','zhongshan road','hunan');
insert into student values('3108015','surui',16,'f','computer-tec','zhongshan road','fujian');
insert into student values('3108016','liushaoqi',24,'m','english','zhongshan road','hunan');

1. sandy老师所教的课程号、课程名称；

select c.cid AS ' 课程号' ,c.cname AS '课程名称' from course c where c.teacher = 'sandy'

1. 年龄大于20岁的女学生的学号和姓名；

select s.sid AS '学号',s.sname AS '名字' from student s where s.sex = 'f' and s.age>20;

1. 在学生表中按性别排序，且男在前女在后显示记录。

SELECT * from student ORDER BY sex DESC;

1. “wuyi”所选修的全部课程名称；

select c.cname from student s, course c, sc 
where s.sname = 'wuyi'
and s.sid = sc.sid
and c.cid = sc.cid;

1. 所有成绩都在80分以上的学生姓名及所在系；

select s.sname,s.department ,sc.grade from student s, course c, sc 
where sc.grade>=80
and s.sid = sc.sid
and c.cid = sc.cid;

#想一下没门成绩都在80分以上的学生信息怎么查

1. 没有选修“english”课的学生的姓名；

select s.sname from student s, course c, sc 
where c.cname = 'english' 
and s.sid = sc.sid
and c.cid = sc.cid;

1. 与“jilian”同乡的男生姓名及所在系；

select * from student s where s.sname  'jilian' and s.birthplace = (select birthplace from student  where sname = 'jilian');

1. 英语成绩比数学成绩好的学生;

select s.sname, sc1.grade as english,sc2.grade as math from student s, course c1, course c2,sc sc1, sc sc2
where c1.cname = 'english' 
and c2.cname = 'math'
and sc1.grade>sc2.grade
and s.sid = sc1.sid
and c1.cid = sc1.cid
and c2.cid = sc2.cid;

1. 选修同一门课程时，女生比所有男生成绩都好的学生名单；

select f.sname
  from (select s.sname,sc.cid, sc.grade
          from student s, sc 
         where s.sid = sc.sid
           and s.sex = 'f') f,
       (select sc.cid, sc.grade
          from student s, sc
         where s.sid = sc.sid
           and s.sex = 'm') m
 where f.cid = m.cid
   and f.grade > m.grade;

1. 至少选修两门及以上课程的学生姓名、性别；

select * from student where sid in (SELECT sid from sc GROUP BY sid having count(1)>1);
select s.sname, s.sex
  from student s, sc
 where s.sid = sc.sid
 group by s.sname, s.sex
having count(distinct sc.cid) > 2;

1. 选修了sandy老师所讲课程的学生人数；

select COUNT(*) from sc where cid in (select cid from course where teacher='sandy')

1. “english”课程得最高分的学生姓名、性别、所在系；

select * from student where sid = (select sid from sc where cid =(select cid from course where cname='english') order by grade Desc LIMIT 0,1);

select * from student s,sc, course c 
where c.cname='english' 
and c.cid = sc.cid
and s.sid = sc.sid
order by grade Desc LIMIT 0,1