SELECT
*
FROM XMLTABLE('field1\field2' columns "field3" varchar2(10) 'field3');

declare
spath varchar2(4000):='field1\field2' ;
begin
for rec (SELECT
*
FROM XMLTABLE(spath columns "field3" varchar2(10) 'field3');) loop
null;
end loop;
end;

WITH T AS (
           SELECT  XMLTYPE('<field1><field2><field3>XYZ</field3></field2></field1>') X,
                   '/field1/field2' PATH
             FROM  DUAL
          )
SELECT  FIELD3
  FROM  T,
        XMLTABLE(
                 PATH
                 PASSING X
                 COLUMNS
                   FIELD3 VARCHAR2(10) PATH 'field3'
                )
/

FIELD3
----------
XYZ

SQL>