XML Generation using a sql query in an efficient way -Help needed urgently

Question

Hi
I am facing the following issue while generating xml using an sql query. I get the below given table using a query.
     CODE      ID      MARK
==================================
1 4 2331 809
2 4 1772 802
3 4 2331 845
4 5 2331 804
5 5 2331 800
6 5 2210 801
I need to generate the below given xml using a query
<data>
<CODE>4</CODE>
<IDS>
<ID>2331</ID>
<ID>1772</ID>
</IDS>
<MARKS>
<MARK>809</MARK>
<MARK>802</MARK>
<MARK>845</MARK>
</MARKS>
</data>
<data>
<CODE>5</CODE>
<IDS>
<ID>2331</ID>
<ID>2210</ID>
</IDS>
<MARKS>
<MARK>804</MARK>
<MARK>800</MARK>
<MARK>801</MARK>
</MARKS>
</data>
Can anyone help me with some idea to generate the above given CLOB message

Answer 1

not sure if this is the right way to do it but
/* Formatted on 10/12/2011 12:52:28 PM (QP5 v5.149.1003.31008) */
WITH data AS (SELECT 4 code, 2331 id, 809 mark FROM DUAL
              UNION
              SELECT 4, 1772, 802 FROM DUAL
              UNION
              SELECT 4, 2331, 845 FROM DUAL
              UNION
              SELECT 5, 2331, 804 FROM DUAL
              UNION
              SELECT 5, 2331, 800 FROM DUAL
              UNION
              SELECT 5, 2210, 801 FROM DUAL)
SELECT TO_CLOB (
             '<DATA>'
          || listagg (xml, '</DATA><DATA>') WITHIN GROUP (ORDER BY xml)
          || '</DATA>')
          xml
  FROM (  SELECT    '<CODE>'
                 || code
                 || '</CODE><IDS><ID>'
                 || LISTAGG (id, '</ID><ID>') WITHIN GROUP (ORDER BY id)
                 || '</ID><IDS><MARKS><MARK>'
                 || LISTAGG (mark, '</MARK><MARK>') WITHIN GROUP (ORDER BY id)
                 || '</MARK></MARKS>'
                    xml
            FROM data
        GROUP BY code)