<hibernate-mapping>
   <class name="myPackage.ProductGroup" table="radProductGroup">
        <id name="id" column="id">
            <generator class="native"/>
        </id>
      <property name="version" column="versionx"/>
        <many-to-one name="document" class="myPackage.Document"/>       
        <property name="productGroupId"/>
        <property name="xml"/>
        <property name="created"/>
   </class>
</hibernate-mapping>

SELECT x.* FROM (SELECT * FROM radProductGroup ORDER BY created DESC) x GROUP BY x.productGroupId;

SELECT productGroupId, max(created) as created FROM radProductGroup GROUP BY productGroupId ORDER BY max(created) DESC;

SELECT productGroupId, max(created) as created FROM radProductGroup GROUP BY productGroupId ORDER BY 2 DESC;