mysql 建立表之间关系 一对一 练习1

创建db5数据库

create database db5 charset=utf8;

use db5;

例一：一个用户只有一个博客
 
    用户表：
    id  name
    1　mike
    2　alex
    3　jack

mysql> create table user(id int primary key auto_increment,name varchar(50) not null);
Query OK, 0 rows affected (0.07 sec)

插入用户记录

mysql> insert into user(name) values('mike'),('alex'),('jack');
Query OK, 3 rows affected (0.01 sec)
Records: 3  Duplicates: 0  Warnings: 0
 
mysql> select * from user;
+----+------+
| id | name |
+----+------+
|  1 | mike |
|  2 | alex |
|  3 | jack |
+----+------+
3 rows in set (0.00 sec)

    博客表
           fk+unique
    id    url         name_id
　 1　xxxx   　　1
 　2　yyyy   　　3
 　3　zzz    　　2

mysql> create table blog(id int primary key auto_increment,
url varchar(50) not null,
name_id int unique,
foreign key(name_id) references user(id) 
on delete cascade 
on update cascade
);
Query OK, 0 rows affected (0.13 sec)

插入记录

mysql> insert into blog(url,name_id) values('xxx',1),('yyyy',3),('zzz',2);
Query OK, 3 rows affected (0.12 sec)
Records: 3  Duplicates: 0  Warnings: 0
 
mysql> select * from blog;
+----+------+---------+
| id | url  | name_id |
+----+------+---------+
|  1 | xxx  |       1 |
|  2 | yyyy |       3 |
|  3 | zzz  |       2 |
+----+------+---------+
3 rows in set (0.00 sec)