oracle xmltable with columns from another table - sql

Question

with oracle xmltable
SELECT u.*
FROM table1
, XMLTable('/abc/def[contract = $count]'
PASSING xmlcol, 1 as "count"
COLUMNS contract integer path 'contract',
oper VARCHAR2(20) PATH 'oper' ) u
This is normally what we do.
Now I need to have "COLUMNS" in above query selected from another tables column for Xpath
something like
{
SELECT u.*
FROM table1
, XMLTable('/abc/def[contract = $count]'
PASSING xmlcol, 1 as "count"
COLUMNS (select xpath from xpath_metadeta )) u
}
Please let me know if this is possible and how?

Answer 1

One option that comes to my mind is dynamic sql and ref cursor.
Something like this:
DECLARE
columnParameters SYS.ODCIVARCHAR2LIST :=
SYS.ODCIVARCHAR2LIST(
'TITLE VARCHAR2(1000) PATH ''title''',
'SUMMARY CLOB PATH ''summary''',
'UPDATED VARCHAR2(20) PATH ''updated''',
'PUBLISHED VARCHAR2(20) PATH ''published''',
'LINK VARCHAR2(1000) PATH ''link/#href'''
);
ref_cursor SYS_REFCURSOR;
cursor_id NUMBER;
table_description DBMS_SQL.DESC_TAB;
column_count NUMBER;
string_value VARCHAR2(4000);
clob_value CLOB;
FUNCTION DYNAMIC_XMLTABLE(xml_columns SYS.ODCIVARCHAR2LIST) RETURN SYS_REFCURSOR
IS
result SYS_REFCURSOR;
statementText VARCHAR2(32000) := Q'|SELECT * FROM
XMLTABLE(
XMLNAMESPACES (DEFAULT 'http://www.w3.org/2005/Atom'),
'for $entry in /feed/entry return $entry'
PASSING
HTTPURITYPE('http://stackoverflow.com/feeds/tag?tagnames=oracle&sort=newest').getxml()
COLUMNS
{column_definition}
)|';
BEGIN
SELECT REPLACE(statementText, '{column_definition}', LISTAGG(COLUMN_VALUE, ', ') WITHIN GROUP (ORDER BY ROWNUM)) INTO statementText FROM TABLE(xml_columns);
DBMS_OUTPUT.PUT_LINE('Statement: ' || CHR(10) || statementText);
OPEN result FOR statementText;
RETURN result;
END;
BEGIN
DBMS_OUTPUT.ENABLE(NULL);
ref_cursor := dynamic_xmltable(columnParameters);
cursor_id := DBMS_SQL.TO_CURSOR_NUMBER(ref_cursor);
DBMS_SQL.DESCRIBE_COLUMNS(cursor_id, column_count, table_description);
FOR i IN 1..column_count LOOP
IF table_description(i).col_type = 1 THEN
DBMS_SQL.DEFINE_COLUMN(cursor_id, i, string_value, 4000);
ELSIF table_description(i).col_type = 112 THEN
DBMS_SQL.DEFINE_COLUMN(cursor_id, i, clob_value);
END IF;
END LOOP;
WHILE DBMS_SQL.FETCH_ROWS(cursor_id) > 0 LOOP
FOR i IN 1..column_count LOOP
DBMS_OUTPUT.PUT_LINE(table_description(i).col_name || ': datatype=' || table_description(i).col_type);
IF (table_description(i).col_type = 1) THEN
BEGIN
DBMS_SQL.COLUMN_VALUE(cursor_id, i, string_value);
DBMS_OUTPUT.PUT_LINE('Value: ' || string_value);
END;
ELSIF (table_description(i).col_type = 112) THEN
BEGIN
DBMS_SQL.COLUMN_VALUE(cursor_id, i, clob_value);
DBMS_OUTPUT.PUT_LINE('Value: ' || clob_value);
END;
-- add other data types
END IF;
END LOOP;
END LOOP;
DBMS_SQL.CLOSE_CURSOR(cursor_id);
END;
I depends how the cursor is consumed. It's much simple if by an application, a bit more difficult if using PL/SQL.