使用Xquery针对递归数据查询？

Question

I am needing to perform a hierarchical query that's rather common in SQL. But now I need to do the same thing upon an xml document using Xquery.

For an example, I'm modeling off a standard Oracle tutorial on its recursive CONNECT BY feature. This is the table, but converted to xml:

<EMPLOYEES>
  <EMP>
    <EMPNO>7369</EMPNO>
    <ENAME>SMITH</ENAME>
    <JOB>CLERK</JOB>
    <MGR>7902</MGR>
    <HIREDATE>17-DEC-80</HIREDATE>
    <SAL>800</SAL>
  </EMP>
  <EMP>
    <EMPNO>7499</EMPNO>
    <ENAME>ALLEN</ENAME>
    <JOB>SALESMAN</JOB>
    <MGR>7698</MGR>
    <HIREDATE>20-FEB-81</HIREDATE>
    <SAL>1600</SAL>
    <COMM>300</COMM>
  </EMP>
  <EMP>
    <EMPNO>7521</EMPNO>
    <ENAME>WARD</ENAME>
    <JOB>SALESMAN</JOB>
    <MGR>7698</MGR>
    <HIREDATE>22-FEB-81</HIREDATE>
    <SAL>1250</SAL>
    <COMM>500</COMM>
  </EMP>
  <EMP>
    <EMPNO>7566</EMPNO>
    <ENAME>JONES</ENAME>
    <JOB>MANAGER</JOB>
    <MGR>7839</MGR>
    <HIREDATE>02-APR-81</HIREDATE>
    <SAL>2975</SAL>
  </EMP>
  <EMP>
    <EMPNO>7654</EMPNO>
    <ENAME>MARTIN</ENAME>
    <JOB>SALESMAN</JOB>
    <MGR>7698</MGR>
    <HIREDATE>28-SEP-81</HIREDATE>
    <SAL>1250</SAL>
    <COMM>1400</COMM>
  </EMP>
  <EMP>
    <EMPNO>7698</EMPNO>
    <ENAME>BLAKE</ENAME>
    <JOB>MANAGER</JOB>
    <MGR>7839</MGR>
    <HIREDATE>01-MAY-81</HIREDATE>
    <SAL>2850</SAL>
  </EMP>
  <EMP>
    <EMPNO>7782</EMPNO>
    <ENAME>CLARK</ENAME>
    <JOB>MANAGER</JOB>
    <MGR>7839</MGR>
    <HIREDATE>09-JUN-81</HIREDATE>
    <SAL>2450</SAL>
  </EMP>
  <EMP>
    <EMPNO>7788</EMPNO>
    <ENAME>SCOTT</ENAME>
    <JOB>ANALYST</JOB>
    <MGR>7566</MGR>
    <HIREDATE>19-APR-87</HIREDATE>
    <SAL>3000</SAL>
  </EMP>
  <EMP>
    <EMPNO>7839</EMPNO>
    <ENAME>KING</ENAME>
    <JOB>PRESIDENT</JOB>
    <HIREDATE>17-NOV-81</HIREDATE>
    <SAL>5000</SAL>
  </EMP>
  <EMP>
    <EMPNO>7844</EMPNO>
    <ENAME>TURNER</ENAME>
    <JOB>SALESMAN</JOB>
    <MGR>7698</MGR>
    <HIREDATE>08-SEP-81</HIREDATE>
    <SAL>1500</SAL>
    <COMM>0</COMM>
  </EMP>
  <EMP>
    <EMPNO>7876</EMPNO>
    <ENAME>ADAMS</ENAME>
    <JOB>CLERK</JOB>
    <MGR>7788</MGR>
    <HIREDATE>23-MAY-87</HIREDATE>
    <SAL>1100</SAL>
  </EMP>
  <EMP>
    <EMPNO>7900</EMPNO>
    <ENAME>JAMES</ENAME>
    <JOB>CLERK</JOB>
    <MGR>7698</MGR>
    <HIREDATE>03-DEC-81</HIREDATE>
    <SAL>950</SAL>
  </EMP>
  <EMP>
    <EMPNO>7902</EMPNO>
    <ENAME>FORD</ENAME>
    <JOB>ANALYST</JOB>
    <MGR>7566</MGR>
    <HIREDATE>03-DEC-81</HIREDATE>
    <SAL>3000</SAL>
  </EMP>
  <EMP>
    <EMPNO>7934</EMPNO>
    <ENAME>MILLER</ENAME>
    <JOB>CLERK</JOB>
    <MGR>7782</MGR>
    <HIREDATE>23-JAN-82</HIREDATE>
    <SAL>1300</SAL>
  </EMP>
</EMPLOYEES>

I am trying to emulate the SYS_CONNECT_BY_PATH function, and produce the Org hierarchy for a given employee. eg for employee ADAMS...

KING JONES SCOTT ADAMS

The linkage is between an emp id and his mgr code.

It looks like a recursive string concatenation function would do the trick, but I'm too new to Xquery and can't get syntax to work.

Part of my cornfusion stems from the notion of 'Hierachy'. This is not the document hierachy that I need to chase. The hierarchy is in the data; rendered more like a linked list.

Any thoughts would be appreciated.

Answer 1

Ideally the XML would be formatted hierarchically, so the organization is implicit in the XML, and all you would need to do is get employee ancestors (or descendants). In this case, you can write a recursive function that follows the path of ID-based links from employee to manager-employee:

declare function local:boss-R(
  $emp as element(EMP)?
) as xs:string*
{
  if (empty($emp)) then ()
  else 
    let $boss := $emp/ancestor::EMPLOYEES/EMP[EMPNO eq $emp/MGR]
    return ($boss/ENAME/string(), local:boss-R($boss))
};

declare function local:org(
  $emp as element(EMP)
) as xs:string+
{
  $emp/ENAME, local:boss-R($emp)
};

let $emp := doc('employees.xml')/EMPLOYEES/EMP[1]
return reverse(local:org($emp))