1、新建主键table
1 create table demo1_zhujian (
2 id int primary key auto_increment,
3 name varchar(10));
2、新建外键table
1 create table demo2_waijian (
2 id int primary key auto_increment,
3 _id int not null default 0,
4 name varchar(10),
5 index (_id),
6 FOREIGN KEY (_id) REFERENCES demo1_zhujian(id) ON DELETE CASCADE ON UPDATE CASCADE);
7
8 create table demo3_waijian (
9 id int primary key auto_increment,
10 _id int not null default 0,
11 name varchar(10),
12 index (_id),
13 FOREIGN KEY (_id) REFERENCES demo1_zhujian(id) ON DELETE CASCADE ON UPDATE CASCADE);
3、添加数据
1 insert into demo1_zhujian
2 (name)
3 values
4 ('11111');
5
6 insert into demo2_waijian
7 (_id, name)
8 values
9 (1, 'demo2_1');
10
11 insert into demo3_waijian
12 (_id, name)
13 values
14 (1, 'demo3_1');
4、查询数据
1 select * from demo1_zhujian;
2 select * from demo2_waijian;
3 select * from demo3_waijian;
5、修改主键数据
1 update demo1_zhujian set id=22 where id=1;
6、重复第4步
外键table中修改外键不行
7、主键table中删除数据
1 delete from demo1_zhujian where id=22;
8、重复第4步
