Collapse down calendar table by grouping like fields - sql

Question

I have a script that generates a calendar table and fills in the public holidays and weekends for England and Wales. I would like to have the non working days as start and end periods, so taking the input
1980-04-01 00:00:00.000 Tuesday 0
1980-04-02 00:00:00.000 Wednesday 0
1980-04-03 00:00:00.000 Thursday 0
1980-04-04 00:00:00.000 Friday 1
1980-04-05 00:00:00.000 Saturday 1
1980-04-06 00:00:00.000 Sunday 1
1980-04-07 00:00:00.000 Monday 1
1980-04-08 00:00:00.000 Tuesday 0
1980-04-09 00:00:00.000 Wednesday 0
It would give the output
Start end
1980-04-03 1980-04-08
in other words, the day before the first non working day and the day after the last non working day of the group. To do this I would presumably use a min and max with a group and dateadd, but how do I go about obtaining a unique number to group each set of days by? This is using 2008 R2.
IF OBJECT_ID('tempdb.dbo.#calendar', 'U') IS NOT NULL
DROP TABLE #calendar
IF OBJECT_ID('tempdb.dbo.#easter', 'U') IS NOT NULL
DROP TABLE #easter;
-- CREATE TABLE CALENDAR
CREATE TABLE #calendar
(
[CalendarDate] DATETIME,
dayofwk varchar(20),
)
DECLARE #StartDate DATETIME
DECLARE #EndDate DATETIME
--INPUTS GO HERE
SET #StartDate = '01-01-1980'
SET #EndDate = '31-12-2018'
DECLARE #Startyear int
DECLARE #endyear int
set #startyear = YEAR(#StartDate)
set #endyear = YEAR(#EndDate)
WHILE #StartDate <= #EndDate
BEGIN
INSERT INTO #calendar
(
CalendarDate, dayofwk
)
SELECT
#StartDate, datename(dw,#startdate)
SET #StartDate = DATEADD(dd, 1, #StartDate)
END
---CREATE LIST OF EASTER MONDAY & GOOD FRIDAYS
create table #easter(
eastersunday_goodfriday date)
DECLARE #y int,
#EpactCalc INT,
#PaschalDaysCalc INT,
#NumOfDaysToSunday INT,
#EasterMonth INT,
#EasterDay INT
WHILE #Startyear <= #endyear
BEGIN
SET #y = #startyear
SET #EpactCalc = (24 + 19 * (#Y % 19)) % 30
SET #PaschalDaysCalc = #EpactCalc - (#EpactCalc / 28)
SET #NumOfDaysToSunday = #PaschalDaysCalc - (
(#Y + #Y / 4 + #PaschalDaysCalc - 13) % 7
)
SET #EasterMonth = 3 + (#NumOfDaysToSunday + 40) / 44
SET #EasterDay = #NumOfDaysToSunday + 28 - (
31 * (#EasterMonth / 4)
)
insert into #easter
SELECT dateadd(d,-2, CONVERT
( SMALLDATETIME,
RTRIM(#Y)
+ RIGHT('0'+RTRIM(#EasterMonth), 2)
+ RIGHT('0'+RTRIM(#EasterDay), 2) ))
insert into #easter
SELECT dateadd(d,1, CONVERT
( SMALLDATETIME,
RTRIM(#Y)
+ RIGHT('0'+RTRIM(#EasterMonth), 2)
+ RIGHT('0'+RTRIM(#EasterDay), 2) ))
SET #Startyear =#Startyear +1
end
select calendardate, dayofwk,
--NEW YEAR'S DAY
case
when day(calendardate) = 1 and month(calendardate) = 1 and dayofwk not in ('Saturday', 'sunday') then 1
when day(calendardate) between 2 and 3 and month(calendardate) = 1 and dayofwk = 'Monday' then 1
--GOOD FRIDAY, EASTER MONDAY
WHEN eastersunday_goodfriday IS NOT NULL THEN 1
--EARLY MAY BANK HOLIDAY
WHEN (datepart(weekday, CALENDARDATE) + ##DATEFIRST - 2) % 7 + 1 = 1
and (datepart(day, CALENDARDATE) - 1) / 7 + 1 = 1
AND MONTH(CALENDARDATE) = 5
THEN 1
--LATE MAY BANK HOLIDAY
WHEN (datepart(weekday, CALENDARDATE) + ##DATEFIRST - 2) % 7 + 1 = 1
and (datepart(day, CALENDARDATE) - 1) / 7 + 1 = 4
AND MONTH(CALENDARDATE) = 5
THEN 1
--LATE AUGUST BANK HOLIDAY
WHEN (datepart(weekday, CALENDARDATE) + ##DATEFIRST - 2) % 7 + 1 = 1
and (datepart(day, CALENDARDATE) - 1) / 7 + 1 = 4
AND MONTH(CALENDARDATE) = 8
THEN 1
--CHRISTMAS DAY
WHEN DAY(CalendarDate) = 25 AND MONTH(CALENDARDATE) = 12 AND dayofwk NOT IN ('SATURDAY', 'SUNDAY') THEN 1
--BOXING DAY
WHEN DAY(CalendarDate) = 26 AND MONTH(CALENDARDATE) = 12 AND dayofwk NOT IN ('SATURDAY', 'SUNDAY') THEN 1
WHEN DAY(CalendarDate) between 27 and 28 AND MONTH(CALENDARDATE) = 12 AND DAYOFWK IN ('MONDAY','TUESDAY') THEN 1
--SAT&SUN
WHEN DATENAME(DW,CALENDARDATE) IN ('SATURDAY','SUNDAY') THEN 1
ELSE 0
end as ISNONWORKINGDAY
from #calendar c
left join #easter e
on c.calendardate = e.eastersunday_goodfriday
ORDER BY C.CALENDARDATE

Answer 1

This seams like a typical island problem. Given what you posted you could do this:
DECLARE #table TABLE (dt DATE, isNonWorkDay BIT);
INSERT #table(dt,isNonWorkDay)
VALUES
('1980-04-01', 0),
('1980-04-02', 0),
('1980-04-03', 0),
('1980-04-04', 1),
('1980-04-05', 1),
('1980-04-06', 1),
('1980-04-07', 1),
('1980-04-08', 0),
('1980-04-09', 0);
SELECT DATEADD(DAY,-1,MIN(t.dt)), DATEADD(DAY,1,MAX(t.dt))
FROM #table t
WHERE t.isNonWorkDay = 1;
Returns: 1980-04-03, 1980-04-08
For multiple islands you could do this:
DECLARE #table TABLE (dt DATE, isNonWorkDay BIT);
INSERT #table(dt,isNonWorkDay)
VALUES
('1980-04-01', 0),
('1980-04-02', 0),
('1980-04-03', 0),
('1980-04-04', 1),
('1980-04-05', 1),
('1980-04-06', 1),
('1980-04-07', 1),
('1980-04-08', 0),
('1980-04-09', 0),
('1980-04-10', 0),
('1980-04-11', 1),
('1980-04-12', 1),
('1980-04-13', 1),
('1980-04-14', 0),
('1980-04-15', 0);
WITH x AS
(
SELECT *, rn = ROW_NUMBER() OVER (ORDER BY t.dt)
FROM #table t
),
xx AS
(
SELECT *, grouper = x.rn - ROW_NUMBER() OVER (ORDER BY x.dt)
FROM x
WHERE x.isNonWorkDay = 1
)
SELECT dtStart = DATEADD(DAY,-1,MIN(xx.dt)), dtend = DATEADD(DAY,1,MAX(xx.dt))
FROM xx
GROUP BY xx.grouper;
Returns:
dtStart dtend
---------- ----------
1980-04-03 1980-04-08
1980-04-10 1980-04-14

Answer 2

You can use the difference of a consecutive numbering of all days and a consecutive numbering of all non-workingdays to use for the grouping.
For a consecutive group of non-workingdays, these differences will all have the same value, and because of the gaps (workingsdays) between the groups, the next group will have a different (higher) value.
For numbering all days, you can use DATEDIFF, for the numbering of non-workingdays you can use ROW_NUMBER. The query could look like this:
WITH
numbering (calendardate, grp_num) AS (
SELECT
calendardate,
DATEDIFF(day, 0, calendardate) - ROW_NUMBER() OVER (ORDER BY calendardate)
FROM YourTable WHERE ISNONWORKINGDAY = 1
)
SELECT
DATEADD(day, -1, MIN(calendardate)) AS StartDate,
DATEADD(day, +1, MAX(calendardate)) AS EndDate
FROM numbering GROUP BY grp_num;