create or replace function get_range_date
(from_dt date default null,to_dt date default null)
return rang_date_tbl_type pipelined is
start_dt date;
end_dt date;
begin
if from_dt>to_dt then
raise_application_error(-20001,'开始日期比结束日期值大');
end if;
if from_dt is null then
start_dt := trunc(sysdate,'mm');
end_dt := last_day(sysdate);
elsif to_dt is null then
start_dt := trunc(from_dt,'mm');
end_dt := last_day(from_dt);
else
start_dt := trunc(from_dt);
end_dt := trunc(to_dt);
end if;
while start_dt <= end_dt loop
pipe row(start_dt);
start_dt := start_dt + 1;
end loop;
return;
end;