它们被称为外键，你可以在网上找到很多教程。例如；
http://www.mysqltutorial.org/mysql-foreign-key/
举个例子：

CREATE TABLE people (
   id int not null auto_increment primary key,
   name varchar(255) not null,       
);

CREATE TABLE phone_numbers (
   id int not null auto_increment primary key,
   people_id int not null,
   phone_number varchar(32) not null,
   FOREIGN KEY fk_ppkey(people_id)
   REFERENCES people(id)
   ON UPDATE CASCADE
   ON DELETE RESTRICT
);

这些线路：

FOREIGN KEY fk_ppkey(people_id) REFERENCES people(id)

将people表的id字段引用到phone numbers表的people\u id表。