consulta para encontrar todas as colunas em uma tabela sem valor nela

SET serveroutput ON;
 DECLARE
  myOwner VARCHAR2(20):='HR';
  myTable VARCHAR2(25):='A';
  CURSOR c2
  IS
    SELECT column_name,
      avg_col_len
    FROM all_tab_columns
    WHERE table_name = myTable
    AND owner        = myOwner;
BEGIN
  FOR r1 IN c2
  LOOP
    IF r1.AVG_COL_LEN =0 THEN
      dbms_output.put_line('column_name = '||r1.column_name);
    END IF;
  END LOOP;
END;