<hibernate-mapping>
  <class name="org.hibernate.test.hbm.propertiesconstraint.Account">
    <id name="id" column="id" type="long">
      <generator class="native" />
    </id>
    <many-to-one name="root"  not-null="false" foreign-key="FKAccountRoot" unique-key="AccountRootCode"/>
    <property name="code">
        <column name="code" sql-type="varchar(255)" not-null="true" unique-key="AccountRootCode" />
    </property>
  </class>
</hibernate-mapping>