CREATE OR REPLACE PACKAGE kscope_ptf AS 
 
  FUNCTION describe (p_tbl  IN OUT DBMS_TF.TABLE_T, 
                     p_cols DBMS_TF.COLUMNS_T ) 
           RETURN DBMS_TF.DESCRIBE_T; 
 
END; 

CREATE OR REPLACE PACKAGE BODY kscope_ptf AS 
 
  FUNCTION describe (p_tbl  IN OUT DBMS_TF.TABLE_T, 
                     p_cols DBMS_TF.COLUMNS_T ) 
           RETURN DBMS_TF.DESCRIBE_T IS 
  BEGIN 
 
    -- for every column in p_tbl... 
    FOR ocounter IN 1..p_tbl.column.count LOOP 
 
      -- set pass_through to FALSE 
      DBMS_OUTPUT.PUT_LINE('Object Column    ' || p_tbl.column(ocounter).description.name); 
      p_tbl.column(ocounter).PASS_THROUGH := FALSE; 
 
      -- for every column in p_col1... 
      FOR rcounter IN 1..p_cols.count LOOP 
 
        -- If requested column matches existing column then pass it on through 
        IF UPPER(p_cols(rcounter)) = UPPER(p_tbl.column(ocounter).description.name) THEN 
          DBMS_OUTPUT.PUT_LINE('Requested Column ' || p_cols(rcounter)); 
          p_tbl.column(ocounter).PASS_THROUGH := TRUE; 
        END IF; 
 
      END LOOP;  -- ever column in p_col1 
 
    END LOOP;  -- every column in p_tab 
 
    RETURN NULL; 
  END; 
 
END; 

CREATE OR REPLACE FUNCTION kscope_func(p_tbl IN TABLE, p_cols DBMS_TF.COLUMNS_T ) 
  RETURN TABLE PIPELINED 
  ROW POLYMORPHIC USING kscope_ptf; 

SELECT * 
  FROM kscope_func(kscope,COLUMNS(year))

SELECT * 
  FROM kscope_func(kscope,COLUMNS(year,city))

SELECT * 
  FROM kscope_func(kscope,COLUMNS(city,not_there))

SELECT * 
  FROM kscope_func(kscope,COLUMNS(not_there))

SELECT * 
  FROM kscope_func(kscope,COLUMNS(city,year))