和另外一张表产生关系
1.节省空间
2.约束,保持一致性
create table userinfo(
uid int auto_increment priority key,
name varchar(32),
department_id int,
constrait fk_user_depar foreign key ("department_id",) references department("id") # 外键
)engine=innodb default charset=utf-8;
creat table department(
id int auto_increment priority key,
title char(15)
)engine=innodb default charset=utf-8;