Yu Xu, thanks for the reply; so far, I haven't seen any objections or
explanations as to why this shouldn't be done. I tested it in Oracle, and it
works. As I understand it, however, this isn't possible in Postgres.
The reason I’m asking is that I need to implement
"XMLType.createXML(CURSOR(...))".
One way to do this is by calling a table-valued function, something like
"createXml((select value from table(toXmlStr(cursor(...)))))", but that seems a
bit unnatural and complex.
That’s what led me to consider cursor support for UDFs. I looked into
`MAP(query)` and `ARRAY(query)`, but they are implemented as special operators
that I wouldn't be able to replicate at runtime or am I mistaken?
Is there perhaps a better overall approach to solving this problem?
Julian Hyde, as I described earlier, I have a task to implement the
UDF(User-Defined Function) "XMLType.createXML(CURSOR(...))" so that one can
write queries like this, for example:
SELECT
d.deptno,
d.dname,
CREATE_XML(
CURSOR(
SELECT
e.empno,
e.ename,
e.job,
e.sal
FROM emp e
WHERE e.deptno = d.deptno
ORDER BY e.ename
)
) AS emp_xml
FROM dept d
ORDER BY d.dname;
