mysql 建立表之间关系 练习 1

练习：账号信息表，用户组，主机表，主机组

#用户表

mysql> create table user(
id int not null unique auto_increment,
username varchar(50) not null,
password varchar(50) not null,
primary key(username,password));
Query OK, 0 rows affected (0.12 sec)

插入用户信息

mysql> insert into user(username,password) values(‘root‘,‘123‘),(‘alex‘,‘1234‘),(‘mike‘,‘1234‘);
Query OK, 3 rows affected (0.01 sec)
Records: 3  Duplicates: 0  Warnings: 0

mysql> select * from user;
+----+----------+----------+
| id | username | password |
+----+----------+----------+
|  1 | root     | 123      |
|  2 | alex     | 1234     |
|  3 | mike     | 1234     |
+----+----------+----------+
3 rows in set (0.09 sec)

#用户组表

mysql> create table usergroup(
id int primary key auto_increment,
groupname varchar(20) not null unique);
Query OK, 0 rows affected (0.21 sec)

mysql> insert into usergroup(groupname) values
(‘IT‘),
(‘sale‘),
(‘Finance‘),
(‘boss‘);
Query OK, 4 rows affected (0.10 sec)
Records: 4  Duplicates: 0  Warnings: 0

mysql> select * from usergroup;
+----+-----------+
| id | groupname |
+----+-----------+
|  4 | boss      |
|  3 | Finance   |
|  1 | IT        |
|  2 | sale      |
+----+-----------+
4 rows in set (0.00 sec)

#主机表

mysql> create table host(
id int primary key auto_increment,
ip char(16) not null unique default ‘127.0.0.1‘);
Query OK, 0 rows affected (0.13 sec

插入ip记录

insert into host(ip) values
(‘172.16.45.2‘),
(‘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‘)
;

#业务线表

mysql> create table business(id int primary key auto_increment,business varchar(20) not null unique);
Query OK, 0 rows affected (0.20 sec)

mysql> insert into business(business) values
    -> (‘轻松贷‘),
    -> (‘随便花‘),
    -> (‘大富翁‘),
    -> (‘穷一生‘)
    -> ;
Query OK, 4 rows affected (0.04 sec)
Records: 4  Duplicates: 0  Warnings: 0

‘

多对多关系练习

’

#建关系：user与usergroup

创建一张user2usergroup表

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)
on delete cascade
on update cascade,
foreign key(group_id) references usergroup(id)
on delete cascade
on update cascade
);

插入记录

mysql> insert into user2usergroup(user_id,group_id) values(1,1),(1,2),(1,3),(1,4),(2,3),(2,4),(3,4);
Query OK, 7 rows affected (0.09 sec)
Records: 7  Duplicates: 0  Warnings: 0

mysql> 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 |
+----+---------+----------+
7 rows in set (0.00 sec)

#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)
on delete cascade
on update cascade,
foreign key(business_id) references business(id)
on delete cascade
on update cascade
);

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

#建关系：user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)
on delete cascade
on update cascade,
foreign key(host_id) references host(id)
on delete cascade
on update cascade
);

insert into user2host(user_id,host_id) values
(1,1),
(1,2),
(1,3),
(1,4),
(2,2),
(2,3),
(2,4),
(2,5),
(3,10),
(3,11),
(3,12)
;

ysql> select * from user2host;
+----+---------+---------+
| id | user_id | host_id |
+----+---------+---------+
|  1 |       1 |       1 |
|  2 |       1 |       2 |
|  3 |       1 |       3 |
|  4 |       1 |       4 |
|  5 |       2 |       2 |
|  6 |       2 |       3 |
|  7 |       2 |       4 |
|  8 |       2 |       5 |
|  9 |       3 |      10 |
| 10 |       3 |      11 |
| 11 |       3 |      12 |
+----+---------+---------+
11 rows in set (0.00 sec)

原文地址：https://www.cnblogs.com/mingerlcm/p/9867670.html