SQL一对一外键关联

 一对一的外键关联实质就是特殊的多对一的外键关联

创建一张人员表

create table tb_person

(

person_id int auto_incremnet,

person_name varchar(50),

primary key (pid)

);

再创建一张身份证的表：

create table tb_card

(

card_id int auto_incremnet,

card_number char(18) not null,

police_station not null,

expir date not null,

person_id int not null,

primary key (card_id)

);

先添加外键约束

alter table tb_card add constraint fk_card_person_id foreign key (person_id) references tb_person (person_id);

再添加唯一性约束

alter table tb_card add constraint uni_card_id unique (person_id);

现在这两张表就拥有一对一的外键关联