[英]Oracle XMLTABLE left outer join doesn't return results when XPath doesn't exist
[英]LEFT OUTER JOIN with XMLTABLE doesn't work?
这是示例查询-
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;
结果我得到-
DNAME ENAME EMPNO
---------- ---------- ----------
Accounting Abraham 1
Accounting Alexander 2
Broking Benjamin 3
Broking Bradley 4
为什么不是dept
的第三行,即 HR 的行没有显示在结果集中? 理想情况下,根据 LEFT JOIN 的规则,应该显示左侧表中的所有记录。 为什么要过滤掉那个?
您以错误的方式进行了外部连接和交叉连接。 您需要将empdata
作为子查询交叉连接到xmltable
,并使用该子查询(内联视图)作为外部连接的目标:
...
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
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