Mysql實現級聯操作（級聯更新、級聯刪除）

原創

2018-09-13 04:51

來源 https://www.cnblogs.com/zxf100/p/6812269.html

一、首先創建兩張表stu，sc

create table stu(
sid int UNSIGNED primary key auto_increment,
name varchar(20) not null)
TYPE=InnoDB charset=utf8;
}
create table sc(
scid int UNSIGNED primary key auto_increment,
sid int UNSIGNED not null,
score varchar(20) default '0',
index (sid),   --外鍵必須加索引
FOREIGN KEY (sid) REFERENCES stu(sid) ON DELETE CASCADE ON UPDATE CASCADE)
TYPE=InnoDB charset=utf8;

}

注意：外鍵建議建立索引；

FOREIGN key(sid) 設置外鍵，把sid設爲外鍵

REFERENCES stu(sid) 引用作用。引用stu表中的sid

ON DELETE CASCADE 級聯刪除
ON UPDATE CASCADE 級聯更新

二、向兩張表插入數據

insert into stu (name) value ('zxf');
insert into stu (name) value ('ls');
insert into stu (name) value ('zs');
insert into stu (name) value ('ww');

insert into sc(sid,score) values ('1','98');
insert into sc(sid,score) values ('1','98');
insert into sc(sid,score) values ('2','34');
insert into sc(sid,score) values ('2','98');
insert into sc(sid,score) values ('2','98');
insert into sc(sid,score) values ('3','56');
insert into sc(sid,score) values ('4','78');
insert into sc(sid,score) values ('4','98');