Max consecutive time_periods by date and hour - sql-server

Question

For a particular exercise I am required to find and locate the maximum consecutive/continuous date and time range. The time_period is given in a format YYYY_MM_DD_hr HH that I converted into YYYY-MM-DD-HH:00:00:000 to enable addition and subtraction operations. The data is a forecast that runs from 2014-2039 and I believe I need to basically 'flag' beginning and end of consecutive periods, ie. 2014-01-01-01:00:00:000 to 2014-01-02:00:00:000 would return a value of '1'. I am using Microsoft SQL Server Management Studio 2012.
So far I have something like:
SELECT r1.Report_Day ,
r1.Report_Hour ,
r1.report_month ,
r1.report_year ,
DATEADD(HOUR, r1.report_hour, CAST(CAST(r1.report_year AS VARCHAR) + '-' + CAST(r1.report_month AS VARCHAR) + '-' + CAST(r1.report_day AS VARCHAR) AS DATETIME)) AS 'NEWDATETIME'

Answer 1

Lets make up some test date ranges:
DECLARE #DateRangeTable TABLE
(
StartDate DATETIME,
EndDate DATETIME
);
INSERT INTO #DateRangeTable
VALUES
( '01-01-2010', '01-31-2010 23:59:00' ),
( '02-01-2010', '02-28-2010 23:59:00' ),
( '03-01-2010', '03-31-2010 23:59:00' ),
( '05-01-2010', '05-31-2010 23:59:00' ),
( '06-01-2010', '06-30-2010 23:59:00' ),
( '01-01-2011', '01-31-2011 23:59:00' ),
( '02-01-2011', '02-28-2011 23:59:00' ),
( '03-01-2011', '03-31-2011 23:59:00' ),
( '04-01-2011', '04-30-2011 23:59:00' ),
( '05-01-2011', '05-31-2011 23:59:00' ),
( '06-01-2011', '06-30-2011 23:59:00' ),
( '01-01-2012', '01-31-2012 23:59:00' ),
( '02-01-2012', '02-28-2012 23:59:00' ),
( '03-01-2012', '03-31-2012 23:59:00' ),
( '04-01-2012', '04-30-2012 23:59:00' ),
( '05-01-2012', '05-31-2012 23:59:00' );
Setup to start searching for our periods
DECLARE #StartDate DATETIME;
SELECT #StartDate = MIN(StartDate) FROM #DateRangeTable;
This part creates a numbers table for all the hours of our range
DECLARE #number_of_numbers INT = 100000;
;WITH
a AS (SELECT 1 AS i UNION ALL SELECT 1),
b AS (SELECT 1 AS i FROM a AS x, a AS y),
c AS (SELECT 1 AS i FROM b AS x, b AS y),
d AS (SELECT 1 AS i FROM c AS x, c AS y),
e AS (SELECT 1 AS i FROM d AS x, d AS y),
f AS (SELECT 1 AS i FROM e AS x, e AS y),
numbers AS
(
SELECT TOP(#number_of_numbers)
ROW_NUMBER() OVER (ORDER BY (SELECT NULL)) AS number
FROM f
),
dt as
(
SELECT dt.CheckHour
FROM
(
SELECT
DATEADD(HOUR, n.number, #StartDate) CheckHour
FROM numbers n
) dt
INNER JOIN #DateRangeTable drt
ON dt.CheckHour >= drt.StartDate AND dt.CheckHour <= drt.EndDate
),
t as
(
SELECT
dt.CheckHour,
ROW_NUMBER() OVER(ORDER BY dt.CheckHour) i
FROM dt
)
We have a couple of CTE expressions above, numbers is numbers table, dt is a list of all the hours based on the date range table, t is just the hours with a rownumber to check against.
SELECT
d.PeriodStart,
d.PeriodEnd,
DATEDIFF(HOUR, d.PeriodStart, d.PeriodEnd) NumOfHours
FROM
(
SELECT
MIN(t.CheckHour) PeriodStart,
MAX(t.CheckHour) PeriodEnd
FROM t
GROUP BY DATEDIFF(HOUR, DATEADD(HOUR, i, 0), t.CheckHour)
) d
So the real code is I first get the difference between the hours - the rownumber to group my records into contiguous ranges and then I get the min and max to get the beginning and end and then just diff the hours to get the longest range based on hours, here is the output:
PeriodStart PeriodEnd NumOfHours
2010-01-01 01:00:00.000 2010-03-31 23:00:00.000 2158
2010-05-01 00:00:00.000 2010-06-30 23:00:00.000 1463
2011-01-01 00:00:00.000 2011-06-30 23:00:00.000 4343
2012-01-01 00:00:00.000 2012-02-28 23:00:00.000 1415
2012-03-01 00:00:00.000 2012-05-31 00:00:00.000 2184

Answer 2

The requirement is not very clear but it seems that something on this lines will work:
select newdatetime, newdatetime -(select max(newdatetime)
from yourtable b where b.newdatetime<a.newdatetime) As Period
from yourtable a
order by newdatetime

Answer 3

Ok. Assuming that you created the NEWDATETIME column and has the complete datetime value as mentioned in the question, try this:
SELECT CONVERT(float, r1_1.NEWDATETIME - MAX(r1_2.NEWDATETIME)) * 24
FROM r1 r1_1
INNER JOIN r1 r1_2 ON r1_2.NEWDATETIME < r1_1.NEWDATETIME
GROUP BY r1_1.NEWDATETIME
This gives you all the differences in Hours. To find the maximum value of all:
SELECT MAX(hoursDiff) FROM (
SELECT CONVERT(float, r1_1.NEWDATETIME - MAX(r1_2.NEWDATETIME)) * 24 hoursDiff
FROM r1 r1_1
INNER JOIN r1 r1_2 ON r1_2.NEWDATETIME < r1_1.NEWDATETIME
GROUP BY r1_1.NEWDATETIME) dt