Add X number of Working days to a date - sql

Question

I have a table PostingPeriod that uses a company calendar to track all working days. Simplified, it looks like this:
Date Year Quarter Month Day IsWorkingDay
25.06.2015 2015 2 6 25 1
26.06.2015 2015 2 6 26 1
27.06.2015 2015 2 6 27 0
I have another table that contains all purchase lines with the Orderdate, confirmed delivery date from the vendor and the maximum allowed timeframe in working days between orderdate and deliverydate:
PurchID OrderDate ConfDelivery DeliveryDays
1234 14.04.2015 20.05.2015 30
1235 14.04.2015 24.05.2015 20
I want to create a new column that returns the maximum allowed Date (regardless of workday or not) for each order. The usual approach (Workingdays / 5 to get weeks, multiplied by 7 to get days) doesn't work, as all holidays etc need to be taken into consideration.
As this is for a DWH that will feed an OLAP database, performance is not an issue.

Answer 1

You could do this by assigning each working day an arbitrary index using ROW_NUMBER, e.g.
SELECT Date, WorkingDayIndex = ROW_NUMBER() OVER(ORDER BY Date)
FROM dbo.Calendar
Which will give you something like:
Date WorkingDayIndex
-----------------------------
2015-04-27 80
2015-04-28 81
2015-04-29 82
2015-04-30 83
2015-05-01 84
2015-05-05 85
2015-05-06 86
2015-05-07 87
Then if you want to know the date that is n working days from a given date, find the date with an index n higher, i.e. 2015-04-27 has an index of 80, therefore 5 working days later would have an index of 85 which yields 2015-05-05.
FULL WORKING EXAMPLE
/***************************************************************************************************************************/
-- CREATE TABLES AND POPULATE WITH TEST DATA
SET DATEFIRST 1;
DECLARE #Calendar TABLE (Date DATE, IsWorkingDay BIT);
INSERT #Calendar
SELECT TOP 365 DATEADD(DAY, ROW_NUMBER() OVER(ORDER BY object_id), '20141231'), 1 FROM sys.all_objects;
UPDATE #Calendar
SET IsWorkingDay = 0
WHERE DATEPART(WEEKDAY, Date) IN (6, 7)
OR Date IN ('2015-01-01', '2015-04-03', '2015-04-06', '2015-05-04', '2015-05-25', '2015-08-31', '2015-12-25', '2015-12-28');
DECLARE #T TABLE (PurchID INT, OrderDate DATE, ConfDeliveryDate DATE, DeliveryDays INT);
INSERT #T VALUES (1234, '20150414', '20150520', 30), (1235, '20150414', '20150524', 20);
/***************************************************************************************************************************/
-- ACTUAL QUERY
WITH WorkingDayCalendar AS
( SELECT *, WorkingDayIndex = ROW_NUMBER() OVER(ORDER BY Date)
FROM #Calendar
WHERE IsWorkingDay = 1
)
SELECT *
FROM #T AS t
INNER JOIN WorkingDayCalendar AS c1
ON c1.Date = t.OrderDate
INNER JOIN WorkingDayCalendar AS c2
ON c2.WorkingDayIndex = c1.WorkingDayIndex + t.DeliveryDays;
If this is a common requirement, then you could just make WorkingDayIndex a fixed field on your calendar table so you don't need to calculate it each time it is required.

Answer 2

Starting from OrderDate, the Date if you advance N(DeliveryDays) WorkingDays.
If i understood correctly you want something like this:
select
PurchID,
OrderDate,
ConfDelivery,
DeliveryDay,
myDays.[Date] myWorkingDayDeliveryDate
from Purchases p
outer apply (
select
[Date]
from (
select
ROW_NUMBER() OVER (
ORDER BY
Date
) myDays,
[Date]
from PostingPeriod pp
where
IsWorkingDay = 1 and
pp.date >= p.OrderDate
) myDays
where
myDays = p.DeliveryDay
) myDays

Answer 3

You'd have to do something like
SELECT OrderDate.PurchId, OrderDate.OrderDate, OrderDate.DeliveryDays, Aux.Counter, Aux.Date
FROM OrderDate, (SELECT row_number() OVER (ORDER BY Date) AS Counter, Date FROM PostingPeriod WHERE IsWorkingDay = 1 ) Aux
WHERE Counter = DeliveryDays
ORDER BY 1
Basically, you'd need all the dates inserted in the table PostingPeriod (weekends and holidays would have a IsWorkingDay = 0, rest of the days = 1)
and this would provide you the minimal date by summing the OrderDate with the ammount of working days