1、新建主鍵table

1 create table demo1_zhujian (
2 id int primary key auto_increment,
3 name varchar(10));

2、新建外來鍵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、新增資料

 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、查詢資料

1 select * from demo1_zhujian;
2 select * from demo2_waijian;
 
3 select * from demo3_waijian;

5、修改主鍵資料

6、重複第4步

外來鍵table中修改外來鍵不行

7、主鍵table中刪除資料

1 delete from demo1_zhujian where id=22;

8、重複第4步