Number of fridays between two dates

Question

How do I find the number of fridays between two dates(including both the dates) using a select statement in oracle sql?

Answer 1

Try modifying this one:

CREATE OR REPLACE FUNCTION F_WORKINGS_DAYS  
(V_START_DATE IN DATE, V_END_DATE IN DATE)

RETURN NUMBER IS
DAY_COUNT NUMBER := 0;
CURR_DATE DATE;

BEGIN -- loop through and update
CURR_DATE := V_START_DATE;
WHILE CURR_DATE <= V_END_DATE
LOOP
    IF TO_CHAR(CURR_DATE,'DY') NOT IN ('SAT','SUN') -- Change this bit to ignore all but Fridays
        THEN DAY_COUNT := DAY_COUNT + 1;
    END IF;
    CURR_DATE := CURR_DATE + 1;
END LOOP;

    RETURN DAY_COUNT;
END F_WORKINGS_DAYS;

/

Answer 2

SELECT (NEXT_DAY('31-MAY-2012','SUN')
-NEXT_DAY('04-MAR-2012','SUN'))/7 FROM DUAL

Answer 3

select sum(case when trim(to_char(to_date('2009-01-01','YYYY-MM-DD')+rownum,'Day')) = 'Friday' then 1 else 0 end) number_of_fridays
from dual
connect by level <= to_date('&end_date','YYYY-MM-DD') - to_date('&start_date','YYYY-MM-DD')+1;

Original source - http://forums.oracle.com/forums/thread.jspa?messageID=3987357&tstart=0

Answer 4

select ((DATEDIFF(dd,@a,@b)) + DATEPART(dw,(@a-6)))/7

Answer 5

This will do it:

select ((next_day(date2-7,'FRI')-next_day(date-1,'FRI'))/7)+1 as num_fridays
from data

Perhaps best if I break that down. The NEXT_DAY function returns the next day that is a (Friday in this case) after the date.

So to find the first Friday after d1 would be:

next_day( d1, 'FRI')

But if d1 is a Friday that would return the following Friday, so we adjust:

next_day( d1-1, 'FRI')

Similarly to find the last Friday up to and including d2 we do:

next_day( d1-7, 'FRI')

Subtracting the 2 gives a number of days: 0 if they are the same date, 7 if they a re a week apart and so on:

next_day( d1-7, 'FRI') - next_day( d1-1, 'FRI') 

Convert to weeks:

(next_day( d1-7, 'FRI') - next_day( d1-1, 'FRI')) / 7

Finally, if they are the same date we get 0, but really there is 1 Friday, and so on so we add one:

((next_day( d1-7, 'FRI') - next_day( d1-1, 'FRI')) / 7) + 1

Answer 6

I have to throw in my two cents for using a calendar table. (It's a compulsion.)

select count(*) as num_fridays
from calendar
where day_of_week = 'Fri'
  and cal_date between '2011-01-01' and '2011-02-17';

num_fridays
-----------
6

Dead simple to understand. Takes advantage of indexes.

Maybe I should start a 12-step group. Calendar Table Anonymous.