在xml(Oracle)中使用命名空间时如何通过xmltable解析xml

I want to parse a xml string that is a web service response sent from servier, the xml looks like this:

<?xml version="1.0" encoding="utf-8"?>
<soap:Envelope xmlns:soap="http://schemas.xmlsoap.org/soap/envelope/" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema">
    <soap:Body>
        <addResponse xmlns="http://tempuri.org/">
            <addResult>20</addResult>
        </addResponse>
    </soap:Body>
</soap:Envelope>

我想在元素addResult之间获得值20.我的plsql代码段如下所示：

declare
  v_xml clob;
begin
  v_xml := '<?xml version="1.0" encoding="utf-8"?>
  <soap:Envelope xmlns:soap="http://schemas.xmlsoap.org/soap/envelope/" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema">
    <soap:Body>
      <addResponse xmlns="http://tempuri.org/">
        <addResult>20</addResult>
      </addResponse>
    </soap:Body>
  </soap:Envelope>';
  for c in (select results 
        from xmltable('Envelope/Body/addResponse' passing xmltype(v_xml) 
        columns results varchar(100) path './addResult')
       )
  loop
    dbms_output.put_line('the result of calculation is : ' || c.results);
  end loop;
end;

seems that nothing was printed out, but if I remove the namespace ‘soap’, the code works well, so can anybody tell me how can I got the value 20 when the xml has namespace?

应该是这样的：

declare    
  v_xml clob;    
begin    
  v_xml := '<?xml version="1.0" encoding="utf-8"?>    
  <soap:Envelope xmlns:soap="http://schemas.xmlsoap.org/soap/envelope/" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema">    
    <soap:Body>    
      <addResponse xmlns="http://tempuri.org/">    
        <addResult>20</addResult>    
      </addResponse>    
    </soap:Body>    
  </soap:Envelope>';    
  for c in (select results    
              from xmltable(xmlnamespaces(default 'http://tempuri.org/',    
                                          'http://schemas.xmlsoap.org/soap/envelope/' as    
                                          "soap" ),    
                            'soap:Envelope/soap:Body/addResponse' passing    
                            xmltype(v_xml) columns results varchar(100) path    
                            './addResult')) loop    
    dbms_output.put_line('the result of calculation is : ' || c.results);    
  end loop;    
end;