Add number of working days to Date in snowflake - snowflake-cloud-data-platform

Question

I'm trying to add no. of business days to a date field.
Below is my logic, this is not working if day falls on Monday and if no. of days are more than 5.
dateadd(DAY,
(iff(dayofweek(to_date(Start_Date_Column) ) = 1, 0 ,
(TRUNCATE(((dayofweek(to_date(Start_Date_Column)) + No_DAYS - 1)/5)) * 2)) + No_DAYS) , to_date(Start_Date_Column));
e.g.. For the below scenario the date is moving to 2021-01-09(which is Saturday) instead of monday(2021-01-11)
select
dateadd(DAY,
(iff(dayofweek(to_date('2021-01-04') ) = 1, 0 ,
(TRUNCATE(((dayofweek(to_date('2021-01-04')) + 5 - 1)/5)) * 2)) + 5) , to_date('2021-01-04'))

Answer 1

Recursive CTE to get next business day, after adding specific number of business days to a date.
WITH RECURSIVE
biz_day (rown, dt) AS
(
SELECT 1,'2022-05-07'::date
union all
SELECT
case when dayname(dateadd(day,1,dt)) not in ('Sat','Sun')
then rown+1
else rown end ,
dateadd(day,1,dt)
from biz_day where rown <= $No_DAYS
)
SELECT min(dt) orig_dt,max(dt) nxt_biz_date FROM biz_day;
ORIG_DT
NXT_BIZ_DATE
2022-05-07
2022-05-20
Original table -
Column next_dy to be modified with next business day, based on specific number of days (e.g. 10)
select * from dates;
DY
NEXT_DY
2022-05-05
NULL
2022-05-09
NULL
2022-05-11
NULL
2022-05-14
NULL
2022-05-15
NULL
2022-05-17
NULL
2022-05-27
NULL
(UDF) Function creation including recursive CTE for getting next biz day -
CREATE OR REPLACE FUNCTION next_b_date(dt date,no_day number)
RETURNS date
LANGUAGE SQL
AS
$$
WITH RECURSIVE
biz_day (rown, cte_dt) AS
(
SELECT 1,dt
union all
SELECT
case when dayname(dateadd(day,1,cte_dt)) not in ('Sat','Sun')
then rown+1
else rown end ,
dateadd(day,1,cte_dt)
from biz_day where rown <= no_day
)
SELECT max(cte_dt) nxt_biz_date FROM biz_day
$$;
Anonymous Block to call function and update source table -
EXECUTE IMMEDIATE $$
DECLARE
p_dt date;
n_dt date;
no_days number;
c1 CURSOR FOR SELECT dy FROM dates;
BEGIN
for record in c1 do
p_dt:=record.dy;
no_days:=10;
n_dt:=(select next_b_date(:p_dt,:no_days));
update dates set next_dy = :n_dt where dy=:p_dt;
end for;
RETURN 0;
END;
$$
;
Table after running the update -
select * from dates;
DY
NEXT_DY
2022-05-05
2022-05-19
2022-05-09
2022-05-23
2022-05-11
2022-05-25
2022-05-14
2022-05-27
2022-05-15
2022-05-27
2022-05-17
2022-05-31
2022-05-27
2022-06-10
Below can also be used, which has little-bit of hard-coding
i.e. multiply number of days with 3 to go bit over extra in days
(to compensate for intermediate sat/sun) for fetching business days.
set no_days=11;
update dates dt1 set next_dy = dt2.n_dy from
(
with cte1 as
(select row_number() over (partition by dy order by seq4()) rn,dy,
dateadd(day,rn,dy) day1 from dates,
table(generator(rowcount=>$no_days*3))), cte2 as
(select row_number() over (partition by dy order by seq4()) rn,dy,day1
from cte1 where dayname(day1)
not in ('Sat','Sun') )
select dy,max(day1) n_dy from cte2 where rn<=$no_days
group by dy order by dy
) dt2
where dt1.dy = dt2.dy;
Table after update -
select * from dates;
DY
NEXT_DY
2022-05-05
2022-05-20
2022-05-09
2022-05-24
2022-05-11
2022-05-26
2022-05-14
2022-05-30
2022-05-15
2022-05-30
2022-05-17
2022-06-01
2022-05-27
2022-06-13
Old - solution (not valid) to add days and move to next Monday -
To get next business day, check if day after adding is sat or sun and if so, get to next Monday using function next_day
Query with some test-data:
with date_cte(bizday) as
(select * from values
('2022-05-05'::date),
('2022-05-11'::date),
('2022-05-14'::date),
('2022-05-15'::date),
('2022-05-21'::date),
('2022-05-27'::date)
)
select bizday orig_date,dayname(bizday) orig_day,
$No_DAYS No_days,
dateadd(day,$No_DAYS,bizday) next_day,
case when dayname(dateadd(day,$No_DAYS,bizday)) = 'Sat'
then next_day(dateadd(day,$No_DAYS,bizday),'Monday')
when dayname(dateadd(day,$No_DAYS,bizday)) = 'Sun'
then next_day(dateadd(day,$No_DAYS,bizday),'Monday')
else dateadd(day,$No_DAYS,bizday) end next_b_day,
dayname(next_b_day) next_b_dayname
from date_cte;
ORIG_DATE
ORIG_DAY
NO_DAYS
NEXT_DAY
NEXT_B_DAY
NEXT_B_DAYNAME
2022-05-05
Thu
10
2022-05-15
2022-05-16
Mon
2022-05-11
Wed
10
2022-05-21
2022-05-23
Mon
2022-05-14
Sat
10
2022-05-24
2022-05-24
Tue
2022-05-15
Sun
10
2022-05-25
2022-05-25
Wed
2022-05-21
Sat
10
2022-05-31
2022-05-31
Tue
2022-05-27
Fri
10
2022-06-06
2022-06-06
Mon
Refer for date-time
Also, you might need to add more here as the definition of a business day can be varied.