SQL query or PL/SQL function to count business days between two dates

The weekend and holidays should be excluded. It is easy to exclude weekends, but the holiday are specific to each place and should be stored in an additional table. I store the holidays in a table HOLIDAYS_VD:

Select the time interval between two dates

The SQL query is adapted from here.

 select count(*) from (
--  select * from (
 select * from (
 select  dayinbetween, to_char( dayinbetween, 'DY' ) weekday from (
 select   startday+level-1 dayinbetween from (
 select startday ,endday-startday diffdays from (
 select   to_date('01.02.2000','DD.MM.YYYY') endday, to_date('29.02.2000','DD.MM.YYYY') startday from dual
 )
 ) connect by level <= diffdays+1
 )
 )where weekday not in ( 'SAT', 'SUN' )--all not weeknds in between
 ) a
 left join  holidays_vd h on a.dayinbetween=h.day
 where h.day is null
 order by dayinbetween; 

It is almost right, but it does not return 0 is the two dates are the same. I did not corrected it and abandoned it because I needed a PL/SQL function. It is below, it is based on the query above and it seems to work fine.

PL/SQL function subtracting dates and exluding weekends and holidays

create or replace PACKAGE indicators AS
TYPE DateListType IS   TABLE OF DATE;
function subtract_business_dates(    startdate DATE,    enddate   DATE) return integer;
END  ;

create or replace PACKAGE BODY  indicators AS
 function subtract_business_dates(
    startdate DATE,
    enddate   DATE) return integer
IS
  result INTEGER:=1;
 
  dateList DateListType:=DateListType();
  difference_days INTEGER;
BEGIN
  difference_days:=trunc(enddate)-trunc(startdate);
  if difference_days<0 then
  RAISE_APPLICATION_ERROR(-20000, 'The first day is after the second date');
  end if;
    if difference_days=0 then
 return 0;
  end if;
 
  dateList.extend(difference_days);
  FOR i IN dateList.first..dateList.last
  LOOP
    dateList(i):=startdate+i;
 
  END LOOP;
  
    select count(*) into result from (
 
   select * from (
    select  dayinbetween, to_char( dayinbetween, 'DY' ) weekday from (
   select  COLUMN_VALUE dayinbetween  from (table(dateList)) 
      )
    )where weekday not in ( 'SAT', 'SUN' )--all not weeknds in between
   ) a
   left join  holidays_vd h on a.dayinbetween=h.day
    where h.day is null
 
   ;
   return result;
END;
END  ;

Some tests to make sure that the function works well. Note, the table with holidays includes a test date 14.02.2000.

select indicators.subtract_business_dates(to_date('01.02.2000','DD.MM.YYYY'),to_date('29.02.2000','DD.MM.YYYY')) from dual;
select indicators.subtract_business_dates(to_date('04.02.2000','DD.MM.YYYY'),to_date('01.02.2000','DD.MM.YYYY')) from dual; --exception

select indicators.subtract_business_dates(to_date('03.02.2000','DD.MM.YYYY'),to_date('03.02.2000','DD.MM.YYYY')) from dual;--thu
select indicators.subtract_business_dates(to_date('03.02.2000','DD.MM.YYYY'),to_date('04.02.2000','DD.MM.YYYY')) from dual;--fri
select indicators.subtract_business_dates(to_date('03.02.2000','DD.MM.YYYY'),to_date('05.02.2000','DD.MM.YYYY')) from dual;--sat
select indicators.subtract_business_dates(to_date('03.02.2000','DD.MM.YYYY'),to_date('06.02.2000','DD.MM.YYYY')) from dual;--sun
select indicators.subtract_business_dates(to_date('03.02.2000','DD.MM.YYYY'),to_date('07.02.2000','DD.MM.YYYY')) from dual;--mon
select indicators.subtract_business_dates(to_date('03.02.2000','DD.MM.YYYY'),to_date('08.02.2000','DD.MM.YYYY')) from dual;--tue


select indicators.subtract_business_dates(to_date('04.02.2000','DD.MM.YYYY'),to_date('04.02.2000','DD.MM.YYYY')) from dual;--fri
select indicators.subtract_business_dates(to_date('04.02.2000','DD.MM.YYYY'),to_date('05.02.2000','DD.MM.YYYY')) from dual;--sat
select indicators.subtract_business_dates(to_date('04.02.2000','DD.MM.YYYY'),to_date('06.02.2000','DD.MM.YYYY')) from dual;--sun
select indicators.subtract_business_dates(to_date('04.02.2000','DD.MM.YYYY'),to_date('07.02.2000','DD.MM.YYYY')) from dual;--mon
select indicators.subtract_business_dates(to_date('04.02.2000','DD.MM.YYYY'),to_date('08.02.2000','DD.MM.YYYY')) from dual;--tue

select indicators.subtract_business_dates(to_date('10.02.2000','DD.MM.YYYY'),to_date('10.02.2000','DD.MM.YYYY')) from dual;--thu
select indicators.subtract_business_dates(to_date('10.02.2000','DD.MM.YYYY'),to_date('11.02.2000','DD.MM.YYYY')) from dual;--fri
select indicators.subtract_business_dates(to_date('10.02.2000','DD.MM.YYYY'),to_date('12.02.2000','DD.MM.YYYY')) from dual;--sat
select indicators.subtract_business_dates(to_date('10.02.2000','DD.MM.YYYY'),to_date('13.02.2000','DD.MM.YYYY')) from dual;--sun
select indicators.subtract_business_dates(to_date('10.02.2000','DD.MM.YYYY'),to_date('14.02.2000','DD.MM.YYYY')) from dual;--mon holiday
select indicators.subtract_business_dates(to_date('10.02.2000','DD.MM.YYYY'),to_date('15.02.2000','DD.MM.YYYY')) from dual;--tue
select indicators.subtract_business_dates(to_date('10.02.2000','DD.MM.YYYY'),to_date('16.02.2000','DD.MM.YYYY')) from dual;--wed