PL/SQL: Count number of nodes in xml

Question

I am working with Oracle.

Is there a way to count the number of nodes (including descendants) within an XML file using PL/SQL?

I would like to be able to save the result as a variable to be used as an upper limit for a loop iterator.

I have the following xml, and I want to count the number of nodes within the row node:

<row>
  <date name="date1" id="101"></date>
  <element1 name="ele1" id="111">
    <stuff></stuff>
    <stuff></stuff>
    <stuff></stuff>
  </element1>
  <element2 name="ele2" id="121"></element2>
  <element3 name="ele3" id="131></element15>
</row>

The result should be 7.

@johnbk I am working with Oracle

The idea here is that after I get the number of nodes I can use it in:

nodeCount := 1;
    FOR i IN 1 .. numNodes
    LOOP
        xpath1 := '/row/*[' || nodeCount || ']/@name';
        SELECT EXTRACT(form_xml, xpath1) as other_name;
        nodeCount := nodeCount +1;
    END LOOP;

Thanks for your help.

Answer 1

I would like to be able to save the result as a variable to be used as an upper limit for a loop iterator.

I guess this is related to your another question ?

You don't need to know the number of nodes as your don't have to explicitly loop xml by yourself. You might be trying to solve your real problem in a suboptimal way.

Below how you can find the number you're looking for with XMLQUERY:

declare
  v_data constant xmltype := xmltype('<row>
  <date name="date1" id="101"></date>
  <element1 name="ele1" id="111">
    <stuff></stuff>
    <stuff></stuff>
    <stuff></stuff>
  </element1>
  <element2 name="ele2" id="121"></element2>
  <element3 name="ele3" id="131"></element3>
  </row>');
  v_count xmltype;
begin
  select xmlquery('count($doc/row/descendant::*)'
          passing v_data as "doc"
          returning content)
    into v_count from dual;
  dbms_output.put_line('count = ' || v_count.getstringval);
end;
/

Answer 2

you could try using the dbms_xmldom package

DECLARE
  l_doc  dbms_xmldom.DOMDocument;
  l_list dbms_xmldom.DOMNodeList;
  l_clob clob;
BEGIN
  l_doc:=dbms_xmldom.newdomdocument(form_xml);
l_list:=dbms_xmldom.getChildNodes(dbms_xmldom.getFirstChild(dbms_xmldom.MakeNode(l_doc)));
  dbms_output.put_line('length='||dbms_xmldom.getLength(l_list));
  dbms_lob.freetemporary(l_clob);
END;

Depending on you Oracle version it can have problems with XML containing more than 64K nodes - see https://forums.oracle.com/forums/thread.jspa?threadID=614453