Oracle之：Function ：numberToDate()

create or replace function numberToDate(i_date in number)
return date
is
      v_date number;
      result date ;
begin
      v_date := i_date;
      if v_date = 0 then
         v_date := null;
      end if;
      result := TO_DATE(v_date, 'J');
      return result;
end numberToDate;