问如何删除MySQL中外键约束中所需的主键？

EN

create database table_test;

use table_test;

create table father(
cod int, 
primary key (cod)
);

create table child(
cod int,
cod_father int,
primary key(cod),
constraint fk_cod_father foreign key (cod_father) references father(cod)
on delete cascade
);

alter table father
drop primary key;