# 7.3.1\. 一對多(one to many) _基于連接表的單向一對多關聯_ 應該優先被采用。請注意，通過指定`unique="true"`，我們可以把多樣性從多對多改變為一對多。 ``` <class name="Person"> <id name="id" column="personId"> <generator class="native"/> </id> <set name="addresses" table="PersonAddress"> <key column="personId"/> <many-to-many column="addressId" unique="true" class="Address"/> </set> </class> <class name="Address"> <id name="id" column="addressId"> <generator class="native"/> </id> </class> ``` ``` create table Person ( personId bigint not null primary key ) create table PersonAddress ( personId not null, addressId bigint not null primary key ) create table Address ( addressId bigint not null primary key ) ```