sELECT XMLElement("PropertySet",
                  XMLATTRIBUTES('3434' "OrderId",
                                 null "DHLCode")) 
                                   FROM DUAL  ;

SQL> sELECT XMLElement("PropertySet",
  2                    XMLATTRIBUTES('3434' "OrderId",
  3                                   null "DHLCode"))
  4                                     FROM DUAL  ;
XMLELEMENT("PROPERTYSET",XMLATTRIBUTES('3434'"ORDERID",NULL"DHLCODE"))
-----------------------------------------------------------------------
<PropertySet OrderId="3434"></PropertySet>

SCOTT@orcl_12.1.0.2.0> SELECT banner FROM v$version
  2  /

BANNER
--------------------------------------------------------------------------------
Oracle Database 12c Enterprise Edition Release 12.1.0.2.0 - 64bit Production
PL/SQL Release 12.1.0.2.0 - Production
CORE	12.1.0.2.0	Production
TNS for 64-bit Windows: Version 12.1.0.2.0 - Production
NLSRTL Version 12.1.0.2.0 - Production

5 rows selected.

SCOTT@orcl_12.1.0.2.0> CREATE TABLE test_tab
  2    (orderidcol    VARCHAR2(30),
  3  	dhlcodecol    VARCHAR2(30))
  4  /

Table created.

SCOTT@orcl_12.1.0.2.0> INSERT ALL
  2    INTO test_tab VALUES ('3434', NULL)
  3    INTO test_tab VALUES ('1212', 'A')
  4    INTO test_tab VALUES ( NULL, 'B')
  5  SELECT * FROM DUAL
  6  /

3 rows created.

SCOTT@orcl_12.1.0.2.0> COMMIT
  2  /

Commit complete.

SCOTT@orcl_12.1.0.2.0> SELECT * FROM test_tab
  2  /

ORDERIDCOL                     DHLCODECOL
------------------------------ ------------------------------
3434
1212                           A
                               B

3 rows selected.

SCOTT@orcl_12.1.0.2.0> SELECT XMLSERIALIZE
  2  	      (CONTENT XMLQUERY
  3  		 ('<Table>
  4  		    {for $i in ora:view("TEST_TAB")/ROW
  5  		       return element PropertySet
  6  			 {attribute OrderId {$i/ORDERIDCOL},
  7  			  attribute DHLCode {$i/DHLCODECOL}}}
  8  		  </Table>'
  9  	       RETURNING CONTENT) AS CLOB INDENT)
 10  FROM   DUAL
 11  /

XMLSERIALIZE(CONTENTXMLQUERY('<TABLE>{FOR$IINORA:VIEW("TEST_TAB")/ROWRETURNELEME
--------------------------------------------------------------------------------
<Table>
  <PropertySet OrderId="3434" DHLCode=""/>
  <PropertySet OrderId="1212" DHLCode="A"/>
  <PropertySet OrderId="" DHLCode="B"/>
</Table>


1 row selected.