ms sql group by 2 hours - sql-server

Question

i have this ms-sql code below, running on sql server 2017:
DECLARE #report_int TABLE
(
atimestamp DATETIME,
adate DATE,
ahour INT,
intvalue INT,
attribute CHAR(254),
total INT
)
INSERT INTO #report_int
SELECT
el.servertimestamp,
cast(el.servertimestamp as date) adate,
(DATEPART(HH,el.servertimestamp)) ahour,
el.intvalue,
el.attributes,
0
FROM
eventlog el
where
el.servertimestamp BETWEEN '6/29/2017'
AND DATEADD(dd, +1, '6/29/2019')
and (attributes LIKE '%N<=>OlympieioIn%' OR attributes LIKE '%N<=>OlympieioOut%')
order by
el.servertimestamp
DECLARE #report TABLE
(
adate datetime,
ahour int,
came_in bigint,
gone_out bigint
)
--fill report with dates and hours
INSERT INTO #report (adate, ahour) SELECT DISTINCT adate, ahour FROM #report_int
--reset
UPDATE #report set came_in = 0, gone_out = 0
--update in totals, min and max times
UPDATE #report SET came_in = i.total from
#report r,
(
select adate, ahour, COUNT(*) total
FROM #report_int
WHERE attribute LIKE 'N<=>OlympieioIn'
GROUP BY adate, ahour
) i
WHERE
i.adate = r.adate
and i.ahour = r.ahour
--update out totals
UPDATE #report SET gone_out = i.total from
#report r,
(
SELECT adate, ahour, COUNT(*) total
FROM #report_int
WHERE attribute LIKE 'N<=>OlympieioOut'
GROUP BY adate, ahour
) i
where
i.adate = r.adate
and i.ahour = r.ahour
select
adate,
ahour,
RIGHT('00'+cast(ahour as varchar),2)+':00 - '+RIGHT('00'+cast(ahour+1 as varchar),2)+':00' timeframe,
came_in,
gone_out
from
#report
This code shows how many people came in or gone out of a building every day. As you can see, the amount of people who come in and go out, are displayed in an hourly grouping.
Below is a screenshot of the executed code.
What i want to do is group these data in a 2-hour grouping.For example, the grouping of the 3rd and 4th hour of the executed code above, will be:
DATE(adate): 2018-05-12
Hour(ahour): 15
Timeframe: 15:00-17:00
came_in: 0
gone_out: 2
Your help will be much appreciated,
thank you.

Answer 1

One way to get a datetime to the last 2 hour slot would be to use:
DATEADD(HOUR, DATEDIFF(HOUR, 0, YourDateColumn) - (DATEDIFF(HOUR, 0, YourDateColumn) % 2), 0)
If we then take some (random) sample data, you get the following:
WITH VTE AS (
SELECT CONVERT(datetime2(0),V.DT) AS DT
FROM (VALUES('2018-07-04T00:11:32'),('2018-07-04T01:17:12'),('2018-07-04T02:00:01'),('2018-07-04T07:49:59'),('2018-07-04T07:59:58'),('2018-07-04T08:00:00')) V(DT))
SELECT DT, DATEADD(HOUR, DATEDIFF(HOUR, 0, DT) - (DATEDIFF(HOUR, 0, DT) % 2), 0) AS DT2h
FROM VTE;
Which returns:
DT DT2h
--------------------------- -----------------------
2018-07-04 00:11:32 2018-07-04 00:00:00.000
2018-07-04 01:17:12 2018-07-04 00:00:00.000
2018-07-04 02:00:01 2018-07-04 02:00:00.000
2018-07-04 07:49:59 2018-07-04 06:00:00.000
2018-07-04 07:59:58 2018-07-04 06:00:00.000
2018-07-04 08:00:00 2018-07-04 08:00:00.000
If you wanted a COUNT by 2 hour slot:
WITH VTE AS (
SELECT CONVERT(datetime2(0),V.DT) AS DT
FROM (VALUES('2018-07-04T00:11:32'),('2018-07-04T01:17:12'),('2018-07-04T02:00:01'),('2018-07-04T07:49:59'),('2018-07-04T07:59:58'),('2018-07-04T08:00:00')) V(DT))
SELECT DATEADD(HOUR, DATEDIFF(HOUR, 0, DT) - (DATEDIFF(HOUR, 0, DT) % 2), 0) AS DT2h, COUNT(DT) AS C
FROM VTE
GROUP BY DATEADD(HOUR, DATEDIFF(HOUR, 0, DT) - (DATEDIFF(HOUR, 0, DT) % 2), 0);
Which returns:
DT2h C
----------------------- -----------
2018-07-04 00:00:00.000 2
2018-07-04 02:00:00.000 1
2018-07-04 06:00:00.000 2
2018-07-04 08:00:00.000 1

Answer 2

I would simply manually create a timetable and join it.
The timetable would have 24 rows (one for each hour) and could look like this:
hour hourtimeframe twohourtimeframe
13 13:00 - 14:00 13:00 - 15:00