Add hours to a date excluding weekends.

Question

Hi
I have to write a function to calculate the SLA Due Date by adding hours to the startDate of a ticket. But it should add HRS by excluding weekend Hours.
SLA Would be in HRS... For example, if Ticket was opened on Friday 4PM and SLA is 24 hours, the SLADUEDate should be Monday 4PM Not Saturday 4PM. 
Moreover if the SLA is 12 hours, The SLADueDate should be 4AM Monday. 
I do not have a date table to accomplish this So i am thinking how to tackle this.
Can anyone help me out with the logic for the function. 
Thanks 
Rajiv 
Rajiv

Answer 1

If creating a calendar table is an option, this is simple:
DECLARE @calendar TABLE (date date, isWeekend bit, isHoliday bit)
INSERT INTO @calendar (date, isWeekend, isHoliday)
VALUES
('2014-09-21',1,0),('2014-09-22',0,0),('2014-09-23',0,0),('2014-09-24',0,0),('2014-09-25',0,0),('2014-09-26',0,0),('2014-09-27',1,0),
('2014-09-28',1,0),('2014-09-29',0,0),('2014-09-30',0,0),('2014-10-01',0,0),('2014-10-02',0,0),('2014-10-03',0,0),('2014-10-04',1,0)
DECLARE @tickets TABLE (ticketID INT IDENTITY, ticketstartDateTime DATETIME)
INSERT INTO @tickets (ticketstartDateTime)
VALUES
('2014-09-23 18:22:33'),('2014-09-24 13:11:54'),('2014-09-25 16:33:14'),('2014-09-26 11:22:33')
SELECT t.*, CONVERT(DATETIME,CONVERT(VARCHAR,c.date,101) + ' ' + CONVERT(varchar,ticketstartDateTime,108)) AS SLADateTime
FROM @tickets t
INNER JOIN @calendar c
ON c.date = (SELECT MIN(date)
FROM @calendar
WHERE date > t.ticketstartDateTime
AND isWeekend = 0
AND isHoliday = 0
If not, try:
DECLARE @tickets TABLE (ticketID INT IDENTITY, ticketstartDateTime DATETIME)
INSERT INTO @tickets (ticketstartDateTime)
VALUES
('2014-09-23 18:22:33'),('2014-09-24 13:11:54'),('2014-09-25 16:33:14'),('2014-09-26 11:22:33')
;WITH rCTE AS (
SELECT DATEADD(DAY,10,GETDATE()) AS date, 10 AS mod
UNION ALL
SELECT DATEADD(DAY,-1,r.date) AS date, mod-1 as mod
FROM rCTE r
WHERE mod > -30
), pCal AS (
SELECT r.*, CASE WHEN h.date IS NOT NULL THEN 1 ELSE 0 END AS isHoliday, CASE WHEN DATEPART(WEEKDAY,r.date) IN (7,1) THEN 1 ELSE 0 END AS isWeekend
FROM rCTE r
LEFT OUTER JOIN (SELECT * FROM holidays(YEAR(GETDATE()))) h
ON r.date = h.date
SELECT t.*, CONVERT(DATETIME,CONVERT(VARCHAR,c.date,101) + ' ' + CONVERT(varchar,ticketstartDateTime,108)) AS SLADateTime
FROM @tickets t
INNER JOIN pCal c
ON c.date = (SELECT MIN(date)
FROM pCal
WHERE date > t.ticketstartDateTime
AND isWeekend = 0
AND isHoliday = 0
Note that Holidays() is a function capable of returning holiday dates for your area.