Grouping incident counts into 5 minute time segments - sql

Question

Hoping someone can assist with how to modify the following SQL to achieve the result shown in desired output. I am not fluent in TSQL but know enough to get this far.
My objectrive is to count my incident data and group into 15 minutes time segments starting at midnight but also include zero (0) where there is no incident data in a particular time segment.
Curent Query#
;With cte As
(SELECT CONVERT (varchar(5),DATEADD(minute, 15 *
(DATEDIFF(minute, '20000101', I.CreateTimestamp) / 15), '20000101'),108)
AS CreationTime, I.IncidentShortReference AS Ref
FROM Incident I
WHERE i.CreateTimestamp between DATEADD(d,-1,GETDATE()) and GETDATE()
)
SELECT CTE.CreationTime, count(CTE.Ref) As Count
FROM cte CTE
GROUP BY CTE.CreationTime
ORDER BY CTE.CreationTime
My result
CreationTime count
00:15 2
01:00 1
01:15 1
01:30 1
01:45 2
02:00 1
02:15 1
02:30 4
(Truncated)
Desired Output
CreationTime count
00:15 2
00:30 0
00:45 0
01:00 1
01:15 1
01:30 1
01:45 2
02:00 1
02:15 1
02:30 4
02:45 0
03:00 0
(Truncated)

Answer 1

This uses a cte creating a record for every timestamp between midnight yesterday and now, with a count for the number of incidents in each range with sample data:
declare #incident table (CreateTimestamp datetime, IncidentShortReference varchar(5))
insert into #incident values ('4/10/2017 11:11:00', 'test')
insert into #incident values ('4/10/2017 11:12:00', 'test')
insert into #incident values ('4/10/2017 11:21:00', 'test')
insert into #incident values ('4/10/2017 11:31:00', 'test')
insert into #incident values ('4/10/2017 13:31:00', 'test')
DECLARE #dt datetime
SELECT #dt = dateadd(d, datediff(d, 0, getdate()), 0) - 1 -- yesterday at midnight
;with cte as
(
select #dt dt
union all
select DATEADD(minute, 15, dt) as Next15
FROM cte
WHERE DATEADD(minute, 15, dt) < GETDATE()
)
select convert(varchar(5), dt, 108) as CreationTime, (select count(*) FROM #incident WHERE CreateTimestamp >= dt and CreateTimestamp < dateadd(mi, 15, dt)) as count
from cte
Sample output from a random interval:

Answer 2

You could create a time interval CTE table like this
WITH TIME_CTE
AS(
SELECT
CAST('20170411 00:15:00' AS DATETIME) AS TimePeriod
UNION ALL
SELECT
DATEADD(MINUTE, 15, TimePeriod)
FROM TIME_CTE
WHERE
DATEADD(MINUTE, 15, TimePeriod) < CAST('20170411 23:59:00' AS DATETIME)
)
SELECT
LEFT(CONVERT(VARCHAR(10),TimePeriod,108), 5)
FROM TIME_CTE
Then join it with your original query
WITH TIME_CTE
AS(
SELECT
CAST('20170411 00:15:00' AS DATETIME) AS TimePeriod
UNION ALL
SELECT
DATEADD(MINUTE, 15, TimePeriod)
FROM TIME_CTE
WHERE
DATEADD(MINUTE, 15, TimePeriod) < CAST('20170411 23:59:00' AS DATETIME)
),
CTE
AS (
SELECT CONVERT (varchar(5),DATEADD(minute, 15 *
(DATEDIFF(minute, '20000101', I.CreateTimestamp) / 15), '20000101'),108)
AS CreationTime, I.IncidentShortReference AS Ref
FROM Incident I
WHERE i.CreateTimestamp between DATEADD(d,-1,GETDATE()) and GETDATE()
)
SELECT TIME_CTE.TimePeriod, SUM(IIF(CTE.Ref IS NULL, 0, 1)) As Count
FROM TIME_CTE
LEFT JOIN CTE ON CTE.CreationTime = TIME_CTE.TimePeriod
GROUP BY TIME_CTE.TimePeriod
ORDER BY TIME_CTE.TimePeriod