12.27日作业

create table student
(
sid varchar(10),
sname varchar(20),
sage int,
ssex int,
primary key(sid)
);
– drop table student;

– 课程表
create table course
(
cid varchar(10),
cname varchar(20),
tid int,
primary key(cid)
);
– drop table course;

– 成绩表
create table sc
(
scid int ,
sid varchar(10),
cid varchar(10),
score numeric(4,1),
primary key(scid)
);
– drop table sc;

– 教师表
create table teacher
(
tid varchar(10),
tname varchar(20),
primary key(tid)
);

insert into student (sid,sname,sage,ssex) values(‘101’,‘zhangsan’,23,1);
insert into student (sid,sname,sage,ssex) values(‘102’,‘lisi’,25,2);
insert into student (sid,sname,sage,ssex) values(‘103’,‘wangwu’,27,1);
insert into student (sid,sname,sage,ssex) values(‘104’,‘zhaoliu’,16,2);
insert into student (sid,sname,sage,ssex) values(‘105’,‘maba’,19,1);

– select sid,sname,sage,ssex from student;

insert into teacher (tid,tname) values(‘1001’,‘李四’);
insert into teacher (tid,tname) values(‘1002’,‘王五’);
insert into teacher (tid,tname) values(‘1003’,‘赵六’);
insert into teacher (tid,tname) values(‘1004’,‘李红’);

– select tid,tname from teacher;

insert into course (cid,cname,tid) values(‘001’,‘语文’,‘1001’);
insert into course (cid,cname,tid) values(‘002’,‘数学’,‘1002’);
insert into course (cid,cname,tid) values(‘003’,‘外语’,‘1003’);

– select cid,cname,tid from course;

insert into sc (scid,sid,cid,score) values(1,‘101’,‘001’,65.5);
insert into sc (scid,sid,cid,score) values(2,‘101’,‘002’,70.0);
insert into sc (scid,sid,cid,score) values(3,‘101’,‘003’,35.5);
insert into sc (scid,sid,cid,score) values(4,‘102’,‘001’,45.5);
insert into sc (scid,sid,cid,score) values(5,‘102’,‘002’,27.5);
insert into sc (scid,sid,cid,score) values(6,‘102’,‘003’,32.5);
insert into sc (scid,sid,cid,score) values(7,‘103’,‘001’,83.0);
insert into sc (scid,sid,cid,score) values(8,‘103’,‘002’,64.5);
insert into sc (scid,sid,cid,score) values(9,‘103’,‘003’,92.5);
insert into sc (scid,sid,cid,score) values(10,‘104’,‘001’,17.5);
insert into sc (scid,sid,cid,score) values(11,‘104’,‘002’,25.5);
insert into sc (scid,sid,cid,score) values(12,‘104’,‘003’,97.5);
insert into sc (scid,sid,cid,score) values(13,‘105’,‘001’,73.5);
insert into sc (scid,sid,cid,score) values(14,‘105’,‘002’,29.5);
insert into sc (scid,sid,cid,score) values(15,‘105’,‘003’,17.5);

– 查询平均成绩大于60分的同学的学号和平均成绩；
SELECT sid,AVG(score) FROM sc GROUP BY sid HAVING AVG(score)>60

– 查询"001"课程比"002"课程成绩高的所有学生的学号；
SELECT a.sid
FROM
(SELECT sid,score s1 FROM sc WHERE cid=‘001’) a join (SELECT sid,score s2 FROM sc WHERE cid=‘002’) b
ON a.sid=b.sid
WHERE a.s1>b.s2

– 查询各科成绩最高和最低的分：以如下形式显示：课程ID，最高分，最低分
SELECT cid 课程ID,MAX(score) 最高分,MIN(score) 最低分 FROM sc GROUP BY cid

– 查询所有课程成绩小于60分的同学的学号、姓名
SELECT s1.sid,s2.sname
FROM sc s1 JOIN student s2
ON s1.sid=s2.sid
GROUP BY s1.sid,s2.sname
HAVING MAX(s1.score)<60
– 查询所有同学的学号、姓名、选课数、总成绩；
SELECT s1.sid,s2.sname,COUNT(s1.cid),sum(s1.score)
FROM sc s1 JOIN student s2
ON s1.sid=s2.sid
GROUP BY s1.sid