数据库练习

分析:

【学生表(关联) ---  班级表(被关联)】  -------->多对一
【课程表(关联) ---  老师表(被关联)】  -------->多对一
【学生表(被关联) ---> 成绩表(关联)  <---课程表(被关联)】  -------->多对多

建表顺序：班级表--->学生表--->老师表--->课程表--->成绩表

班级表

create table class(cid int primary key auto_increment,caption varchar(10))

---

老师表

create table teacher(tid int primary key auto_increment,tname varchar(10));

---

学生表

create table student(
sid int primary key auto_increment,
sname varchar(10),
gender varchar(3),
class_id int,
foreign key(class_id) references class(cid) 
on delete cascade 
on update cascade);

---

课程表

create table course(
cid int primary key auto_increment,
cname varchar(10),
teaacher_id int,
foreign key(teaacher_id) references teacher(tid) 
on delete cascade 
on update cascade);

---

分数表

create table score(
sid int primary key auto_increment,
student_id int,
corse_id int,
number int,
foreign key(student_id) references student(sid) 
on delete cascade 
on update cascade,
foreign key(corse_id) references course(cid) 
on delete cascade 
on update cascade);