How count of numbers id for a period of time - sql

Question

I am looking for a way to count the number of id in a period of time every 30 minutes.
I wrote a SQL query, but the result is incorrect
CREATE TABLE [dbo].[#tabl]
(
[Id] [varchar](100) NULL,
[TIMEStart] [datetime] NULL,
[TIMEEnd] [datetime] NULL
) ON [PRIMARY]
INSERT INTO [dbo].[#tabl] VALUES ('1', '2020-04-01 00:05:00.000', '2020-04-01 00:10:00.000')
INSERT INTO [dbo].[#tabl] VALUES ('2', '2020-04-01 00:11:00.000', '2020-04-01 00:29:00.000')
INSERT INTO [dbo].[#tabl] VALUES ('3', '2020-04-01 00:12:00.000', '2020-04-01 00:55:00.000')
WITH CTE AS
(
SELECT
[Id],
DATEADD(MINUTE, (DATEDIFF(MINUTE, [TIMEStart], [TIMEEnd]) / 30) * 30, 0) AS RangeTime
FROM
[dbo].[#tabl]
GROUP BY
[Id], DATEADD(MINUTE, (DATEDIFF(MINUTE, [TIMEStart],[TIMEEnd]) / 30) * 30, 0)
)
SELECT numreq, RangeTime
FROM
(SELECT COUNT(DISTINCT id) AS numreq, RangeTime
FROM CTE
GROUP BY RangeTime) temp
Correct result - table:
numreq RangeTime
-------------------------------------
3 1900-01-01 00:00:00.000
1 1900-01-01 00:30:00.000
Period of time:
1900-01-01 00:00:00.000 - includes 3 id:1, 2, 3
1900-01-01 00:30:00.000 - includes 1 id:1

Answer 1

I think what you need is to create a list of RangeTime values that lie within the range of the TIMEStart and TIMEEnd values in tabl (which you can do with a recursive CTE), then you can JOIN that list back to tabl on an overlapping time range and count the number of rows that overlap each RangeTime:
WITH CTE AS (
SELECT DATEADD(MINUTE,(DATEDIFF(MINUTE, 0, MIN([TIMEStart]))/30)*30,0) as RangeTime,
MAX([TIMEEnd]) AS MaxTime
FROM [dbo].[tabl]
UNION ALL
SELECT DATEADD(MINUTE, 30, RangeTime), MaxTime
FROM CTE
WHERE DATEADD(MINUTE, 30, RangeTime) < MaxTime
)
SELECT RangeTime, COUNT(tabl.Id) AS numreq
FROM CTE
LEFT JOIN tabl ON tabl.TIMEStart < DATEADD(MINUTE, 30, RangeTime)
AND RangeTime <= tabl.TIMEEnd
GROUP BY RangeTime
Output:
RangeTime numreq
2020-04-01T00:00:00Z 3
2020-04-01T00:30:00Z 1
Demo on SQLFiddle
Note: I've presumed you want the actual time for the range, not times starting at the beginning of 1900...