<class name="SubjectAddress" table="SUBJECT_ADDRESS"
     discriminator-value="0">
     <id name="id" column="SUBJECT_ADDRESS_ID" type="integer">
         <generator class="native"/>
     </id>
     <discriminator column="ADDRESS_TYPE" type="integer"/>
     <property name="subjectId" column="SUBJECT_ID" type="integer"                         
         not-null="true" />
     <property name="addressId" column="ADDRESS_ID" type="integer"             
         not-null="true" />
      <subclass
         name="com.rn.mapping.SubjectAddressPostal"
         discriminator-value="2"/>
</class>

<class name="com.rn.mapping.Person" table="PERSON" lazy="true">
     ...
     <one-to-one name="subjectPostalAddress"
    class="com.rn.mapping.SubjectAddressPostal"
    property-ref="subjectId"/>   
</class>

left outer join SUBJECT_ADDRESS subjectaddr on
person.SUBJECT_ID=subjectaddr.SUBJECT_ID and
[b]subjectaddr.ADDRESS_TYPE=3[/b]