# Function to adjust weekend and Holiday in Oracle SQL

Hello,

I have a requirement to calculate due date based on the condition below. Could someone please assist on how to create a function?

Thank you

If Type = Forward {
If the Input Date falls on weekend then
Move the date to following Monday.
Else
Keep the date as is.
If derived date after weekend calculation is a federal holiday (Check if the date is in the table Holiday)
Move the date one day forward and perform the check again to make sure adjusted date is not a weekend or federal holiday.
Else
Keep the date as is.
}
If the Input Date falls on weekend then
Move the date to Friday before.
Else
Keep the date as is.
If derived date after weekend calculation is a federal holiday (Check if the date is in the table Holiday )
Move the date one day back and perform the check again to make sure adjusted date is not a weekend or federal holiday.
Else
Keep the date as is.
}}
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Commented:
You probably wil have to adjust the reference to the holidays. I assumed
CREATE TABLE HOLIDAYS (holiday date);
I chose for a straight forward solution that  wil not be the fastest . Try if its fast enough for you.
You can tweek the max .

CREATE OR REPLACE FUNCTION AdjustDtForFedHoliday (Input Date, Type VARCHAR2)
RETURN VARCHAR2
IS
max_holidays pls_integer := 31;
v_return_date date;
BEGIN
If Type = 'Forward'  THEN
SELECT MIN(NEXT_DAY)
INTO v_return_date
FROM
(SELECT input + (level - 1) NEXT_DAY
FROM DUAL CONNECT BY LEVEL < max_holidays) NEXT_DAYS
WHERE not TO_CHAR(NEXT_DAY,'DY','NLS_DATE_LANGUAGE = AMERICAN') IN ('SAT','SUN')  -- omit weekend
--AND NOT EXISTS (SELECT 1 FROM HOLIDAYS WHERE TRUNC(HOLIDAYS.HOLIDAY) = TRUNC(NEXT_DAYS.NEXT_DAY));  -- trunc omits hours etc.. from input
AND NOT EXISTS (SELECT 1 FROM HOLIDAYS WHERE HOLIDAYS.HOLIDAY = NEXT_DAYS.NEXT_DAY)
;
ELSE
SELECT MAX(PREVIOUS_DAY)
INTO v_return_date
FROM
(SELECT input - (level - 1) PREVIOUS_DAY
FROM DUAL CONNECT BY LEVEL < max_holidays) PREVIOUS_DAYS
WHERE not TO_CHAR(PREVIOUS_DAY,'DY','NLS_DATE_LANGUAGE = AMERICAN') IN ('SAT','SUN')  -- omit weekend
--AND NOT EXISTS (SELECT 1 FROM HOLIDAYS WHERE TRUNC(HOLIDAYS.HOLIDAY) = TRUNC(PREVIOUS_DAYS.PREVIOUS_DAY));  -- trunc omits hours etc.. from input
AND NOT EXISTS (SELECT 1 FROM HOLIDAYS WHERE HOLIDAYS.HOLIDAY = PREVIOUS_DAYS.PREVIOUS_DAY)
;
END IF;
RETURN v_return_date;
END;
/

with this_years_dates
as
(select trunc(SYSDATE,'YYYY') + (level - 1)  input_day
FROM DUAL CONNECT BY LEVEL < 400
)
from this_years_dates
/
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Commented:
Sorry.  My code had a bug so I deleted it.  It was almost exactly what flow01 had posted.

I purposely didn't look at their code before writing mine.  I should have looked at it before posting...  sorry.
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Author Commented:
This is exactly what I looking for. Thank you so much
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