Using dbms_xmlgen with a CAST statement

Question

The following code populates a plsql collection and then attempts to select from it using dbms_xmlgen.
the following error results --
DECLARE
ERROR at line 1:
ORA-19206: Invalid value for query or REF CURSOR parameter
ORA-06512: at "SYS.DBMS_XMLGEN", line 83
ORA-06512: at line 56
The query is correct as the commented out select at end of block works fine.
Can dbms_xmlgen be used in such a way and if not is there a workaround.
Thanks
DECLARE
types declared on the database
create or replace type bus_tab_obj AS object
( BUSINESS_MODEL_ID NUMBER(10)
,BUSINESS_MODEL_VER_NO NUMBER(5)
,BUSINESS_MODEL_NAME VARCHAR2(30));
create or replace TYPE bus_table AS TABLE of bus_tab_obj;
package level variable bus_table_recs in package get_values_pkg
myxml sys.xmltype;
queryCtx DBMS_XMLGen.ctxhandle;
BEGIN
-- initialise and delete
get_values_pkg.bus_table_recs := bus_table(NULL,NULL,NULL);
get_values_pkg.bus_table_recs.DELETE;
-- select some records to put in the collection
for x in ( select BUSINESS_MODEL_ID
,BUSINESS_MODEL_VER_NO
,BUSINESS_MODEL_NAME
from BRK_BUSINESS_MODEL )
LOOP
get_values_pkg.bus_table_recs.extend;
get_values_pkg.bus_table_recs := bus_table(bus_tab_obj(x.business_model_id
,x.business_model_ver_no
,x.business_model_name));
END LOOP;
-- retrieve the records from the collection as xml
queryCtx := DBMS_XMLGen.newContext('select a.business_model_name data from THE ( select cast( get_values_pkg.bus_table_recs as bus_table ) from dual ) a order by data');
dbms_xmlgen.setMaxRows(queryCtx,1);
myxml := DBMS_XMLGen.getXMLType(queryCtx);
dbms_output.put_line(myxml.extract('/*').getStringVal());
this works!
for x in ( select a.business_model_name data
from THE ( select cast( get_values_pkg.bus_table_recs as bus_table ) from dual ) a
order by data )
loop
dbms_output.put_line( x.data );
end loop;
END;
/

Answer 1

891794 wrote:
Thank you all , see I am new to this database field , I am not a pro.Not a problem. However, one of the very first things you should learn is that dynamic SQL is seldom needed and invariably just plain wrong.
If a table name is dynamic, or a column name is dynamic - then chances are excellent that your data model is already fubar'ed (or malema'ed to put it in a za.org perspective).
And even when you are in the very exceptional situation where dynamic SQL is needed, SQL injection is a MAJOR security concern.. and almost always ignored by implementing shoddy code to create and execute the dynamic SQL.