数据准备：
## 学院表
create table department(
d_id int primary key auto_increment,
d_name varchar(20) not null
);
insert into department(d_name ) values('计算机学院'),('外语学院');
insert into department(d_name ) values('机械学院'),('建工学院'),('艺术学院');
## 学生表
create table student(
s_id int primary key auto_increment,
s_name varchar(20) not null,
dept_id int ,
foreign key(dept_id) references department(d_id)
);
insert into student(s_name,dept_id ) values('佳能',2),('lucky',3);
insert into student(s_name,dept_id ) values('张三',1),('李四',1);
insert into student(s_name,dept_id ) values('张三丰',2),('小明',3),('小红',2);
insert into student(s_name) values('安迪'),('杰克');
## 学生详情
create table student_detail(
id int primary key, #学号
age int ,
sex char(4),
address varchar(20),
foreign key(id) references student(s_id)
);
insert into student_detail value(4,18,'女','北京');
insert into student_detail value(2,20,'男','湖南长沙');
insert into student_detail value(3,19,'男','广东佛山');
insert into student_detail value(1,21,'男','湖南长沙');
insert into student_detail value(5,17,'女','四川成都');
insert into student_detail value(6,23,'女','湖北武汉');
## 课程表
create table `cours`(
c_id int primary key auto_increment,
c_name varchar(20),
dept_id int not null, # 课程所属学院
foreign key(dept_id) references department(d_id)
);
insert into cours(c_name ,dept_id) values('python',1),('英语',2);
insert into cours(c_name ,dept_id) values('java',1),('工程造价',4);
insert into cours(c_name ,dept_id) values('机械设计',3),('土木',4);
## 选课表
create table `select`(
s_id int,
c_id int,
primary key(s_id,c_id),
foreign key(s_id) references student(s_id),
foreign key(c_id) references cours(c_id)
);
insert into `select` values(2,4),(3,2),(1,1);
insert into `select` values(2,1),(4,2),(3,1);
insert into `select` values(2,3),(4,1),(2,2);
