SQL Oracle XML 空标签和属性

Question

我对 SQL/XML 和 Oracle 有疑问。我将 Oracle 中的示例与 dept 和 emp 一起使用。一开始的情况:我想要一个带有部门和员工的 xml:

SELECT Xmlelement("employees", dept.deptno, Xmlagg(
       Xmlelement("employee", ename))).
       getStringVal()
FROM   emp
       INNER JOIN dept
               ON dept.deptno = emp.deptno
GROUP  BY dept.deptno; 

现在我想要所有部门，即使没有任何员工(右外连接)。此外，我想要员工的一些属性:

SELECT XMLELEMENT("employees", dept.deptno, 
       Xmlagg(
        XMLELEMENT("employee",
             xmlattributes(empno AS "empno", sal AS "salary"), ename)
        )
        ).getStringVal()
FROM   emp
       right outer join dept
                     ON dept.deptno = emp.deptno
GROUP  BY dept.deptno; 

但是现在没有员工的部门有一个空标签“员工”。我有一个解决这个问题的方法:

SELECT           xmlelement("employees", 
                    xmlattributes(dept.deptno as "Abt"), 
                    xmlagg( xmlforest(ename AS "employee") )
                 ).getstringval()
FROM             emp
RIGHT OUTER JOIN dept
ON               dept.deptno = emp.deptno
GROUP BY         dept.deptno;

现在我没有空标签，但我无法放置我想要的属性。这个问题有解决办法吗？

最好的问候 session

Answer 1

您可以使用 case 表达式来不生成流氓 <employee/>节点在第一位:

SELECT XMLELEMENT("employees", dept.deptno, 
         Xmlagg(
           CASE WHEN emp.empno IS NOT NULL THEN
             XMLELEMENT("employee",
               xmlattributes(empno AS "empno", sal AS "salary"), ename)
           END
         )
       ).getStringVal()
FROM   emp
       right outer join dept
                     ON dept.deptno = emp.deptno
GROUP  BY dept.deptno; 

XMLELEMENT("EMPLOYEES",DEPT.DEPTNO,XMLAGG(CASEWHENEMP.EMPNOISNOTNULLTHENXMLELEMENT("EMPLOYEE",XMLATTRIBUTES(EMPNOAS"EMPNO",SALAS"SALARY"),ENAME)END)).GETSTRINGVAL()
--------------------------------------------------------------------------------------------------------------------------------------------------------------------
<employees>10<employee empno="7839" salary="5000">KING</employee><employee empno="7934" salary="1300">MILLER</employee><employee empno="7782" salary="2450">CLARK</employee></employees>
<employees>20<employee empno="7566" salary="2975">JONES</employee><employee empno="7876" salary="1100">ADAMS</employee><employee empno="7369" salary="800">SMITH</employee><employee empno="7902" salary="3000">FORD</employee><employee empno="7788" salary="3000">SCOTT</employee></employees>
<employees>30<employee empno="7698" salary="2850">BLAKE</employee><employee empno="7900" salary="950">JAMES</employee><employee empno="7844" salary="1500">TURNER</employee><employee empno="7654" salary="1250">MARTIN</employee><employee empno="7521" salary="1250">WARD</employee><employee empno="7499" salary="1600">ALLEN</employee></employees>
<employees>40</employees>