-- https://docs.oracle.com/en/database/oracle/oracle-database/23/sqlrf/XMLDIFF.html
SELECT XMLDIFF(
XMLTYPE('<?xml version="1.0"?>
<bk:book xmlns:bk="http://example.com">
   <bk:tr>
        <bk:td>
                <bk:chapter>
                        Chapter 1.
                </bk:chapter>
        </bk:td>
        <bk:td>
                 <bk:chapter>
                        Chapter 2.
                </bk:chapter>
        </bk:td>
   </bk:tr>
</bk:book>'),
XMLTYPE('<?xml version="1.0"?>
<bk:book xmlns:bk="http://example.com">
   <bk:tr>
        <bk:td>
                <bk:chapter>
                        Chapter 1.
                </bk:chapter>
        </bk:td>
        <bk:td/>
   </bk:tr>
</bk:book>')
)
FROM DUAL;