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  • 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)



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  • 原文地址:https://www.cnblogs.com/mingerlcm/p/9866466.html
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