LEFT OUTER JOIN with XMLTABLE doesn't work? - oracle

Question

Here is the sample query-
WITH empdata AS (SELECT xmltype ('<office>
<emp>
<empno>1</empno>
<ename>Abraham</ename>
<deptno>10</deptno>
</emp>
<emp>
<empno>2</empno>
<ename>Alexander</ename>
<deptno>10</deptno>
</emp>
<emp>
<empno>3</empno>
<ename>Benjamin</ename>
<deptno>20</deptno>
</emp>
<emp>
<empno>4</empno>
<ename>Bradley</ename>
<deptno>20</deptno>
</emp>
</office>') AS xcol FROM dual),
dept AS
(SELECT 10 deptno, 'Accounting' dname FROM dual
UNION ALL
SELECT 20, 'Broking' FROM dual
UNION ALL
SELECT 30, 'HR' FROM dual)
SELECT d.dname, e.ename, e.empno
FROM dept d
CROSS JOIN empdata e_data
LEFT OUTER JOIN
xmltable (
'office/emp'
PASSING e_data.xcol
COLUMNS deptno NUMBER (28, 0) PATH 'deptno',
ename VARCHAR2 (10) PATH 'ename',
empno NUMBER (28, 0) PATH 'empno') e
ON d.deptno = e.deptno;
Result I'm getting-
DNAME ENAME EMPNO
---------- ---------- ----------
Accounting Abraham 1
Accounting Alexander 2
Broking Benjamin 3
Broking Bradley 4
Why isn't the third row from dept, i.e. that of HR isn't showing in the result set? Ideally according to the rules of a LEFT JOIN all the records from the table in the left should show. Why is that one being filtered out?

Answer 1

You have the outer join and cross join the wrong way round. You need to cross-join empdata to xmltable as a subquery, and use that subquery (inline view) as the target for the outer join:
...
SELECT d.dname, e.ename, e.empno
FROM dept d
LEFT OUTER JOIN
(
SELECT x.*
FROM empdata e_data
CROSS JOIN
xmltable (
'office/emp'
PASSING e_data.xcol
COLUMNS deptno NUMBER (28, 0) PATH 'deptno',
ename VARCHAR2 (10) PATH 'ename',
empno NUMBER (28, 0) PATH 'empno') x
) e
ON d.deptno = e.deptno;
DNAME ENAME EMPNO
---------- ---------- ----------
Accounting Abraham 1
Accounting Alexander 2
Broking Benjamin 3
Broking Bradley 4
HR