# 7.3.1\. 一对多(one to many) _基于连接表的单向一对多关联_ 应该优先被采用。请注意，通过指定`unique="true"`，我们可以把多样性从多对多改变为一对多。 ``` <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 ) ```