Return NullVal from XMLtype ???

Question

Hi.
When I execute a query:
        WITH t AS (
          SELECT XMLType( CURSOR( select ID, NAME
                                  from Table
                                  ) ) as XXX,
          SELECT XMLType( CURSOR( select ID, NAME
                                  from Table2
                                  ) ) as KKK
          FROM dual
        SELECT XMLQuery(
        '<messages>
         for $i in $XXX/ROWSET/ROW
         return element {$i/NAME} { attribute id {$i/ID},
         for $Z in $KKK/ROWSET/ROW
         return element {$Z/NAME} { attribute id {$Z/ID},
        </messages>'
        passing t.XXX as "XXX",
                   t.KKK AS "KKK"
        returning content
        ).getclobval()
        FROM t
        ;And my TABLE1 return nothing because is empty or don't have a value, Oracle return an error:
ORA-06502: PL/SQL: error of number or value
ORA-06512: a "SYS.XMLTYPE", line 334
ORA-06512: a line 1
There is a condition if return null?
Thanks.
Best regards.
Edited by: city_andre on 7-mar-2011 9.31

Answer 1

Hi,
Yes, that's a drawback of using the CURSOR XMLType constructor...
You can also use DBMS_XMLGEN.getXMLType with each query as a string, but you won't be able to use bind variables :
SELECT XMLQuery(
'<messages>
for $i in $XXX/ROWSET/ROW
return element {$i/NAME} { attribute id {$i/ID},
for $Z in $KKK/ROWSET/ROW
return element {$Z/NAME} { attribute id {$Z/ID},
</messages>'
passing DBMS_XMLGEN.getXMLType('select ID, NAME from Table1') as "XXX",
        DBMS_XMLGEN.getXMLType('select ID, NAME from Table2') as "KKK"
returning content
).getclobval()
FROM t
;Or maybe, consider SQL/XML functions to generate the same XML contents from relational data (as suggested in a previous thread).