XML document must have a top level element. Error

Question

Hi, I am trying to generate an XML. Below is a sample code from my function. The function generates a 0 byte file which when I try to open gives me 'xml document must have a top level element' error. Any ideas?
FUNCTION generateXml(    p_1      VARCHAR2,
                         p_2      VARCHAR2,
                         p_3      VARCHAR2
                         ) RETURN CLOB
IS
    ctx dbms_xmlgen.ctxHandle;
    xml CLOB;
    v_sql varchar2(2000);
BEGIN
lv_sql:=' select * from v_dc where rownum =1';
ctx := dbms_xmlgen.newContext(v_sql);
dbms_xmlgen.setRowSetTag(ctx, 'CONTENT');
xml := dbms_xmlgen.getXML(ctx);
return xml;
END;
END generateXml;

Answer 1

I just need to understand if we can generate XML from a sql that has sub-queries in it.Should be no problem:
SQL> create or replace function generatexml (p_1 varchar2, p_2 varchar2, p_3 varchar2)
  return clob
is
  ctx     dbms_xmlgen.ctxhandle;
  xml     clob;
  v_sql   varchar2 (2000);
begin
  v_sql := ' select * from dept left outer join (select * from emp) emp on (emp.deptno = dept.deptno) where rownum = 1';
  ctx := dbms_xmlgen.newcontext (v_sql);
  dbms_xmlgen.setrowsettag (ctx, 'CONTENT');
  xml := dbms_xmlgen.getxml (ctx);
  dbms_xmlgen.closecontext (ctx);
  return xml;
end generatexml;
Function created.
SQL> select generatexml (null, null, null) xml from dual
XML                                                                            
<?xml version="1.0"?>                                                          
<CONTENT>                                                                      
<ROW>                                                                         
  <DEPTNO>10</DEPTNO>                                                          
  <DNAME>ACCOUNTING</DNAME>                                                    
  <LOC>NEW YORK</LOC>                                                          
  <EMPNO>7782</EMPNO>                                                          
  <ENAME>CLARK</ENAME>                                                         
  <JOB>MANAGER</JOB>                                                           
  <MGR>7839</MGR>                                                              
  <HIREDATE>09.06.81</HIREDATE>                                                
  <SAL>2450</SAL>                                                              
  <DEPTNO>10</DEPTNO>                                                          
</ROW>                                                                        
</CONTENT>                                                                     
1 row selected.Maybe your query simply doesn't return any rows?