现在有一教学管理系统，具体的关系模式如下：
Student (no, name, sex, birthday, class)
Teacher (no, name, sex, birthday, prof, depart)
Course (cno, cname, tno)
Score (no, cno, degree)
其中表中包含如下数据：
Course表：
Score表：
Student表：
Teacher表：
根据上面描述完成下面问题：
DDL
1.
写出上述表的建表语句。
create table Student(
no int,
name varchar(14),
sex varchar(13),
birthday varchar(30),
class varchar(20)
)
create table Teacher(
no int,
name varchar(14),
sex varchar(13),
birthday varchar(30),
prof varchar(16),
depart varchar(20)
)
create table Course(
cno varchar(20),
cname varchar(20),
tno int
)
create table Score(
no int,
cno varchar(20),
degree int
)DML
2. 给出相应的INSERT语句来完成题中给出数据的插入。
insert into Course values
('3-101','数据库',1)
insert into Course values
('5-102','数学',3)
insert into Course values
('3-103','信息系统',4)
insert into Course values
('3-104','操作系统',6)
insert into Course values
('3-105','数据结构',4)
insert into Course values
('3-106','数据处理',5)
insert into Course values
('4-107','pascal语言',5)
insert into Course values
('4-108','c++',7)
insert into Course values
('4-109','java',8)
insert into Course values
('3-245','数据挖掘',10)
insert into Course values
('3-111','软件工程',11)
insert into Score values
(5001,'3-105',69)
insert into Score values
(5001,'5-102',55)
insert into Score values
(5003,'4-108',85)
insert into Score values
(5004,'3-105',77)
insert into Score values
(5005,'3-245',100)
insert into Score values
(5006,'3-105',53)
insert into Score values
(5003,'4-109',45)
insert into Score values
(5008,'3-105',98)
insert into Score values
(5004,'4-109',68)
insert into Score values
(5010,'3-105',88)
insert into Score values
(5003,'3-105',98)
insert into Score values
(5005,'4-109',68)
insert into Score values
(5002,'3-105',88)
insert into Score values
(107,'3-105',98)
insert into Score values
(108,'4-109',68)
insert into Score values
(109,'3-105',88)
insert into Score values
(107,'3-111',88)
insert into Score values
(5003,'3-111',80)
insert into Student values
(5001,'李勇','男','1987-7-22',95001)
insert into Student values
(5002,'刘晨','女','1987-11-1',95002)
insert into Student values
(5003,'王敏','女','1987-10-5',95001)
insert into Student values
(5004,'李好尚','男','1987-9-25',95003)
insert into Student values
(5005,'李军','男','1987-7-17',95004)
insert into Student values
(5006,'范新位','女','1987-6-18',95005)
insert into Student values
(5007,'张霞东','女','1987-8-29',95006)
insert into Student values
(5008,'赵薇','男','1987-6-15',95007)
insert into Student values
(5009,'钱民将','女','1987-6-23',95008)
insert into Student values
(5010,'孙俪','女','1987-9-24',95002)
insert into Student values
(108,'赵里','男','1987-6-15',95007)
insert into Student values
(109,'丘处机','男','1987-6-23',95008)
insert into Student values
(107,'杨康','男','1987-9-24',95001)
insert into Teacher values
(1,'李卫','男','1957-11-5','教授','电子工程系')
insert into Teacher values
(2,'刘备','男','1967-10-9','副教授','math')
insert into Teacher values
(3,'关羽','男','1977-9-20','讲师','sc')
insert into Teacher values
(4,'李修','男','1957-6-25','教授','elec')
insert into Teacher values
(5,'诸葛亮','男','1977-6-15','教授','计算机系')
insert into Teacher values
(6,'殷素素','女','1967-1-5','副教授','sc')
insert into Teacher values
(7,'周芷若','女','1947-2-23','教授','sc')
insert into Teacher values
(8,'赵云','男','1980-6-13','副教授','计算机系')
insert into Teacher values
(9,'张敏','女','1985-5-5','助教','sc')
insert into Teacher values
(10,'黄蓉','女','1967-3-22','副教授','sc')
insert into Teacher values
(11,'张三','男','1967-3-22','副教授','sc')
查询：
3.
输出成绩为85或86或88或在60-80之间的记录（no,cno,degree）
命令：
select no,cno,degree
from Score
where degree in (85,86,88) or (degree >= 60 and degree <=80);
结果：
4. 输出‘3-105’号课程的平均分
命令：
select cast (avg(degree) as numeric(8,6))
from score
where cno = '3-105';
结果：
#注意cast和numeric的用法
5. 输出’95001’班级所选课程的课程号和平均分
命令：
select cno,avg(degree)
from score join student on score.no=student.no
where class =95001
group by cno;
结果：
#注意：
1. group by 上可用where；
2.select后的属性要么包含在group by 后，要么是聚集函数；
3.有聚集函数一定要有group by;
6.
列出“计算机系”教师所教课程的成绩表（课程编号，课程名，学生名，成绩）
命令：
select course.cno,cname,student.name,degree
from student,teacher,course,score
where student.no=score.no and score.cno=course.cno and
course.tno=teacher.no and depart='计算机系';
结果：
#注意：多表查询时（1）在from语句中用join...on...连接
（2）在where语句中每个连接之间要有and