SQL to return the number of working days between 2 passed in dates

Question

I need to write an sql query that returns the number of Working days (Monday - Friday) between two given dates.

I was wondering what would be the most efficient way

Answer 1

Here you go...

1. First check how many days you got in the holiday table, excluding weekend days.

2. Get business days (MON to FRI) between the 2 dates and after that subtract the holiday days.

   create or replace
   FUNCTION calculate_business_days (p_start_date IN DATE, p_end_date IN DATE)
           RETURN NUMBER IS
           v_holidays     NUMBER;
           v_start_date   DATE   := TRUNC (p_start_date);
           v_end_date     DATE   := TRUNC (p_end_date);
           BEGIN
           IF v_end_date >= v_start_date
           THEN
                   SELECT COUNT (*)
                   INTO v_holidays
                   FROM holidays
                   WHERE day BETWEEN v_start_date AND v_end_date
                   AND day NOT IN (
                           SELECT hol.day 
                           FROM holidays hol 
                           WHERE MOD(TO_CHAR(hol.day, 'J'), 7) + 1 IN (6, 7)
                   );
   
           RETURN   GREATEST (NEXT_DAY (v_start_date, 'MON') - v_start_date - 2, 0)
                +   (  (  NEXT_DAY (v_end_date, 'MON')
                        - NEXT_DAY (v_start_date, 'MON')
                       )
                     / 7
                    )
                  * 5
                - GREATEST (NEXT_DAY (v_end_date, 'MON') - v_end_date - 3, 0)
                - v_holidays;
           ELSE
                   RETURN NULL;
           END IF;
   END calculate_business_days;
   

After that you can test it out, like:

    select 
            calculate_business_days('21-AUG-2013','28-AUG-2013') as business_days 
    from dual;