Can't update query table

Hi,
Every time I try to update a query table in my form there will be error

"ORA-00971: missing SET keyword"

this is not happen when I update a table that not use query

here is my define in  dbforms-config.xml

    <query name="view_regis_activity" from="DSS_ACTIVITY_REGIS left join DSS_SUB_ACTIVITY on DSS_SUB_ACTIVITY.SUB_ID = DSS_ACTIVITY_REGIS.SUB_ID">

        <field name="DSS_SUB_ACTIVITY.SUB_ID" fieldType="varchar2" size="5" isKey="true"/>
        <field name="DSS_ACTIVITY_REGIS.REGISTER_USER_ID" fieldType="varchar2" size="120" sortable="true"/>
        <field name="DSS_SUB_ACTIVITY.SUB_NAME_TH" fieldType="varchar2" size="120" sortable="true"/>
        <field name="DSS_SUB_ACTIVITY.SUB_NAME_EN" fieldType="varchar2" size="120" sortable="true"/>
        <field name="DSS_SUB_ACTIVITY.ACTIVITY_ID" fieldType="varchar2" size="120" sortable="true" isKey="true"/>
        <field name="DSS_SUB_ACTIVITY.FEE" fieldType="number" size="22"/>
        <field name="DSS_ACTIVITY_REGIS.STATUS_ID" fieldType="varchar2" size="3" isKey="true"/>
           
    </query>

and use it in jsp file

<db:dbform followUp="/paticipate_detail.jsp" maxRows="*" name="changStatusTable" tableName="view_regis_activity" filter="<%=user_sql2%>" orderBy="DSS_SUB_ACTIVITY.ACTIVITY_ID" autoUpdate="true">
<db:header/>
<db:body>
  .............
</db:body>
<db:footer>
<db:updateButton caption="submit"/>
</db:footer>

is the logical query is not updateable?