create table part(
nid int not null  auto_increment  primary key,
caption varchar(32) not null
);

create table person(
nid int not null auto_increment,
name varchar(32) not null,
email varchar(32) not null,
part_nid int not null,
primary key (nid),
constraint fk_person_part foreign key (part_nid) references part(nid)
);

alter table person drop foreign key fk_person_part; #删除外键
alter table person add constraint fk_per_t1 foreign key (part_nid) references part(nid);  #添加外键

#找到CEO部门的所有人员姓名

select
    person.name,
    part.caption
from
    person
left join part on person.part_nid = part.nid
where
    part.caption = ‘CEO‘