Zkuste toto:
declare
jo JSON_OBJECT_T;
i NUMBER;
keys JSON_KEY_LIST;
CURSOR c_json IS
SELECT myJsonCol FROM mytable;
begin
FOR rec IN c_json
LOOP
jo := JSON_OBJECT_T.parse(rec.myJsonCol);
keys := jo.get_keys;
dbms_output.put_line('KEY VAL');
FOR i in 1..keys.COUNT
LOOP
dbms_output.put_line(keys(i) || ' ' || jo.get_Number(keys(i)));
END LOOP;
END LOOP;
END;
/