General query to recurse through XML nested elements

Question

Hi all,
Using 10g database...and I'm trying to parse XML (stored as clob, no registered schema) that handles nesting and reoccurring of the same element.
i.e.
<Policy ID="1">
<Risk ID="1.1">
<Risk ID="1.1.1">
<Risk ID="1.1.1.1">
</Risk>
</Risk>
</Risk>
<Risk ID="1.2">
</Risk>
<Risk ID="1.3">
<Risk ID="1.3.1">
</Risk>
</Risk>
</Policy>
The "Risk" element can be nested over and over again (and reoccur). Now, I want to combine each child, grandchild, great grandchild..... "Risk" element to the Policy element.
i.e resultset has two columns - policyID, riskID
Next, I'd like to be able to tie each Risk to it's parent Risk
i.e. resultset has two columns - parentRiskID, childRiskID
I know how to handle reoccurring and "known" hierarchies by using the XMLTYPE/PASSING techniques in the FROM clause but I'm struggling with the nesting part because I don't how deep it can go....This would seem to be fairly common in XML.
Any ideas ?
Thanks,
Kevin

Answer 1

Does this help
SQL> var xmltext varchar2(4000)
SQL> --
SQL> begin
  2    :xmltext := '<Policy ID="1">
  3  <Risk ID="1.1">
  4  <Risk ID="1.1.1">
  5  <Risk ID="1.1.1.1">
  6  </Risk>
  7  </Risk>
  8  </Risk>
  9  <Risk ID="1.2">
10  </Risk>
11  <Risk ID="1.3">
12  <Risk ID="1.3.1">
13  </Risk>
14  </Risk>
15  </Policy>';
16  end;
17  /
PL/SQL procedure successfully completed.
SQL> select POLICY_ID, PARENT_RISK_ID, CHILD_RISK_ID
  2    from xmltable
  3         (
  4            '/Policy'
  5            passing xmltype(:xmltext)
  6            columns
  7            POLICY_ID number(4) path '@ID',
  8            RISKS     xmltype   path '//Risk'
  9         ) r,
10         xmltable
11         (
12           '/Risk'
13           passing RISKS
14           columns
15           PARENT_RISK_ID varchar2(40) path '@ID',
16           CHILD_RISK_ID varchar2(40) path 'Risk/@ID'
17         )
18  /
POLICY_ID PARENT_RISK_ID                           CHILD_RISK_ID
         1 1.1                                      1.1.1
         1 1.1.1                                    1.1.1.1
         1 1.1.1.1
         1 1.2
         1 1.3                                      1.3.1
         1 1.3.1
6 rows selected.
SQL> select POLICY_ID, PARENT_RISK_ID, CHILD_RISK_ID
  2    from xmltable
  3         (
  4            '/Policy'
  5            passing xmltype(:xmltext)
  6            columns
  7            POLICY_ID number(4) path '@ID',
  8            RISKS     xmltype   path '//Risk'
  9         ) r,
10         xmltable
11         (
12           '/Risk'
13           passing RISKS
14           columns
15           PARENT_RISK_ID varchar2(40) path '@ID',
16           CHILD_RISK_ID varchar2(40) path 'Risk/@ID'
17         )
18   where CHILD_RISK_ID is not null
19  /
POLICY_ID PARENT_RISK_ID                           CHILD_RISK_ID
         1 1.1                                      1.1.1
         1 1.1.1                                    1.1.1.1
         1 1.3                                      1.3.1
SQL>
SQL>