-- https://docs.oracle.com/en/database/oracle/oracle-database/23/lnpls/plsql-triggers.html
BEGIN
  FOR j IN (SELECT d, old_obj, new_obj FROM tbl_history) LOOP
    DBMS_OUTPUT.PUT_LINE (
      j.d ||
      ' -- old: ' || j.old_obj.n || ' ' || j.old_obj.m ||
      ' -- new: ' || j.new_obj.n || ' ' || j.new_obj.m
    );
  END LOOP;
END;
/