[英]Oracle XMLTABLE left outer join doesn't return results when XPath doesn't exist
[英]LEFT OUTER JOIN with XMLTABLE doesn't work?
這是示例查詢-
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;
結果我得到-
DNAME ENAME EMPNO
---------- ---------- ----------
Accounting Abraham 1
Accounting Alexander 2
Broking Benjamin 3
Broking Bradley 4
為什么不是dept
的第三行,即 HR 的行沒有顯示在結果集中? 理想情況下,根據 LEFT JOIN 的規則,應該顯示左側表中的所有記錄。 為什么要過濾掉那個?
您以錯誤的方式進行了外部連接和交叉連接。 您需要將empdata
作為子查詢交叉連接到xmltable
,並使用該子查詢(內聯視圖)作為外部連接的目標:
...
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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