mysql 外键约束举例

废话少说，直接上代码：

create table policy 

(

    id int not null unique auto_increment primary key,

    name varchar(40) not null,

    description varchar(255)

);

create table policy_profit

(

    id int not null unique auto_increment primary key,

    policy_id INT not null,

     time char(40) not null,

    profit float not null

     

);

alter table policy_profit add CONSTRAINT C1 foreign key (policy_id) references policy(id) on delete CASCADE