MySQL--练习

目录

• 一、练习
  • 创建用户表
  • 用户组表
  • 主机表
  • 业务线表
  • 建关系：user与usergroup
  • 建关系：uesr与host
• 二、作业
  • 1. 建班级表
  • 2. 建学生表
  • 3. 建老师表
  • 4. 建课程表
  • 5. 建成绩表
  • 6. 查询成绩

一、练习

创建用户表

 create table user(id int not null unique auto_increment,
    -> username varchar(20) not null,
    -> password varchar(20) not null,
    -> primary key(username,password)
    -> );
    
 insert into user values(null,'root','123'),
    -> (null,"egon","456"),
    -> (null,"alex","alex3714");
    
select *from user;
+----+----------+----------+
| id | username | password |
+----+----------+----------+
|  1 | root     | 123      |
|  2 | egon     | 456      |
|  3 | alex     | alex3714 |
+----+----------+----------+

用户组表

create table usergroup(id int primary key auto_increment,
    -> groupname varchar(20) not null unique);
    
insert into usergroup(groupname) values("IT"),
    -> ("Sale"),
    -> ("Finance"),
    -> ("Boss");
Query OK, 4 rows affected (1.83 sec)
Records: 4  Duplicates: 0  Warnings: 0

select *from usergroup;
+----+-----------+
| id | groupname |
+----+-----------+
|  4 | Boss      |
|  3 | Finance   |
|  1 | IT        |
|  2 | Sale      |
+----+-----------+

主机表

create table host(id int primary key auto_increment,
    -> ip char(15) not null unique default "127.0.0.1");
    
insert into host(ip) values("127.16.45.2"),
    -> ("172.16.31.10"),("172.16.45.3"),("172.16.31.11"),
    -> ("172.10.45.3"),("172.10.45.4"),("172.10.45.5"),
    -> ("192.168.1.20"),("192.168.1.21"),("192.168.1.22"),
    -> ("192.168.2.23"),("192.168.2.223"),("192.168.2,24"),
    -> ("192.168.3.22"),("192.168.3.23"),("192.168.3.24");
    
select *from host;
+----+---------------+
| id | ip            |
+----+---------------+
|  1 | 127.16.45.2   |
|  5 | 172.10.45.3   |
|  6 | 172.10.45.4   |
|  7 | 172.10.45.5   |
|  2 | 172.16.31.10  |
|  4 | 172.16.31.11  |
|  3 | 172.16.45.3   |
|  8 | 192.168.1.20  |
|  9 | 192.168.1.21  |
| 10 | 192.168.1.22  |
| 13 | 192.168.2,24  |
| 12 | 192.168.2.223 |
| 11 | 192.168.2.23  |
| 14 | 192.168.3.22  |
| 15 | 192.168.3.23  |
| 16 | 192.168.3.24  |
+----+---------------+

业务线表

 create table business(id int primary key auto_increment,
    -> business varchar(20) not null unique);

insert into business(business) values("轻松贷"),("随便花"),("大富翁"),("穷一生");

select *from business;                                          ,"穷一生");生");
+----+-----------+
| id | business  |
+----+-----------+
|  3 | 大富翁     |
|  4 | 穷一生     |
|  1 | 轻松贷     |
|  2 | 随便花     |
+----+-----------+

建关系：user与usergroup

 create table user2usergroup(id int not null unique auto_increment,
    -> user_id int not null,
    -> group_id int not null,
    -> primary key(user_id,group_id),
    -> foreign key(user_id) references user(id),
    -> foreign key(group_id) references usergroup(id)
    -> );                       
                             
insert into user2usergroup(user_id,group_id) values(1,1),
    -> (1,2),
    -> (1,3),
    -> (1,4),
    -> (2,3),
    -> (2,4),
    -> (3,4);
    
 select *from user2usergroup;
+----+---------+----------+
| id | user_id | group_id |
+----+---------+----------+
|  1 |       1 |        1 |
|  2 |       1 |        2 |
|  3 |       1 |        3 |
|  4 |       1 |        4 |
|  5 |       2 |        3 |
|  6 |       2 |        4 |
|  7 |       3 |        4 |
+----+---------+----------+

建关系：host与business

 create table host2business(id int not null unique auto_increment,
    -> host_id int not null,
    -> business_id int not null,
    -> primary key(host_id,business_id),
    -> foreign key(host_id) references host(id),
    -> foreign key(business_id) references business(id)
    -> );

insert into host2business(host_id,business_id) values
    -> (1,1),
    -> (1,2),
    -> (1,3),
    -> (2,2),
    -> (2,3),
    -> (3,4);

select *from host2business;
+----+---------+-------------+
| id | host_id | business_id |
+----+---------+-------------+
|  1 |       1 |           1 |
|  2 |       1 |           2 |
|  3 |       1 |           3 |
|  4 |       2 |           2 |
|  5 |       2 |           3 |
|  6 |       3 |           4 |
+----+---------+-------------+

建关系：uesr与host

create table user2host(
    -> id int not null unique auto_increment,
    -> user_id int not null,
    -> host_id int not null,
    -> primary key(user_id,host_id),
    -> foreign key(user_id) references user(id),
    -> foreign key(host_id) references host(id));


insert into user2host(user_id,host_id) values(
    -> (1,1),
    -> (1,2),
    -> (1,3),
    -> (1,4),
    -> (1,5),
    -> (1,6),
    -> (1,7),
    -> (1,8),
    -> (1,9),
    -> (1,10),
    -> (1,11),
    -> (1,12),
    -> (1,13),
    -> (1,14),
    -> (1,15),
    -> (1,16),
    -> (2,2),
    -> (2,3),
    -> (2,4),
    -> (2,5),
    -> (3,10),
    -> (3,11),
    -> (3,12);
    
select * from user2host;
+----+---------+---------+
| id | user_id | host_id |
+----+---------+---------+
|  1 |       1 |       1 |
|  2 |       1 |       2 |
|  3 |       1 |       3 |
|  4 |       1 |       4 |
|  5 |       1 |       5 |
|  6 |       1 |       6 |
|  7 |       1 |       7 |
|  8 |       1 |       8 |
|  9 |       1 |       9 |
| 10 |       1 |      10 |
| 11 |       1 |      11 |
| 12 |       1 |      12 |
| 13 |       1 |      13 |
| 14 |       1 |      14 |
| 15 |       1 |      15 |
| 16 |       1 |      16 |
| 17 |       2 |       2 |
| 18 |       2 |       3 |
| 19 |       2 |       4 |
| 20 |       2 |       5 |
| 21 |       3 |      10 |
| 22 |       3 |      11 |
| 23 |       3 |      12 |
+----+---------+---------+

二、作业

按照如下表的设计写出SQL语句

1. 建班级表

create table class(
    cid int primary key auto_increment,
    caption varchar(20) not null
);

insert into class(caption) values("三年级二班"),("一年级三班"),("三年级一班");

select *from class;
+-----+-----------------+
| cid | caption         |
+-----+-----------------+
|   1 | 三年级二班        |
|   2 | 一年级三班        |
|   3 | 三年级一班        |
+-----+-----------------+

2. 建学生表

create table student(
    sid int primary key auto_increment,
    sname char(10) not null,
    gender enum('男','女'),
    class_id int not null,
    foreign key(class_id) references class(cid)
);

insert into student(sname,gender,class_id) values
	("钢蛋","女",1),
	("铁锤","女",1),
	("山炮","男",2);
	
select *from student;
+-----+--------+--------+----------+
| sid | sname  | gender | class_id |
+-----+--------+--------+----------+
|   1 | 钢蛋    | 女     |        1 |
|   2 | 铁锤    | 女     |        1 |
|   3 | 山炮    | 男     |        2 |
+-----+--------+--------+----------+

3. 建老师表

create table teacher(
    tid int primary key auto_increment,
    tname varchar(20) not null
);

insert into teacher(tname) values("egon"),("nick"),("jerry");

select *from teacher;
+-----+-------+
| tid | tname |
+-----+-------+
|   1 | egon  |
|   2 | nick  |
|   3 | jerry |
+-----+-------+

4. 建课程表

create table course(
    cid int primary key auto_increment,
    cname char(20) not null,
    teacher_id int not null,
    foreign key(teacher_id) references teacher(tid)
);

insert into course(cname,teacher_id) values
    ("生物",1),
    ("体育",1),
    ("物理",2);

select * from course;
+-----+--------+------------+
| cid | cname  | teacher_id |
+-----+--------+------------+
|   1 | 生物    |          1 |
|   2 | 体育    |          1 |
|   3 | 物理    |          2 |
+-----+--------+------------+

5. 建成绩表

create table score(
    sid int not null unique auto_increment,
    student_id int not null,
    course_id int not null,
    score int not null,
    primary key(student_id,course_id),
    foreign key(student_id) references student(sid),
    foreign key(course_id) references course(cid)
);

insert into score(student_id,course_id,score) values
    (1,1,60),
    (1,2,59),
    (2,2,100);
    
select *from score;
+-----+------------+-----------+-------+
| sid | student_id | course_id | score |
+-----+------------+-----------+-------+
|   1 |          1 |         1 |    60 |
|   2 |          1 |         2 |    59 |
|   3 |          2 |         2 |   100 |
+-----+------------+-----------+-------+

6. 查询成绩

select score from score where student_id = ( ;
    select sid from student where sname="钢蛋") 
    and course_id =(
    select cid from course where cname = "生物");
+-------+
| score |
+-------+
|    60 |
+-------+