Query to select a count group by time period - sql

Question

I have a typical log table with many details and a datetime of when the record was created.
I'm trying to analyse how many times does an event occurs per a time period (each 30 mins). I need to be able to analyze for a period bigger than one day. Basically, my desired output would be something like:
Period | Total
Day 1 00:00 - 00:30 | 23
Day 1 00:30 - 01:00 | 0
Day 1 01:00 - 01:30 | 534
...
Day 2 23:00 - 23:30 | 23
I'm flexible on the date column layout - I just need to be "readable"!
Here's my try but it's not working very well
declare #startdatetime datetime = '2016-02-03 00:00:00'
declare #enddatetime datetime = '2016-02-19 23:59:59'
declare #apiserviceid int = 21
select DATEPART(MINUTE, usr.STARTDATETIME) % 30, COUNT(*)
from TABLE 1 usr
where usr.APIREQUESTID = #apiserviceid
and usr.STARTDATETIME >= #startdatetime and usr.STARTDATETIME <= #enddatetime
group by
(DATEPART(MINUTE, usr.STARTDATETIME) % 30)
order by 1;
Thanks :)

Answer 1

DATEPART(MINUTE,...) are just the minutes within one hour, not the minutes within one day. Consider the hours as well
select (60 * DATEPART(HOUR, usr.STARTDATETIME) +
DATEPART(MINUTE, usr.STARTDATETIME)) % 30, COUNT(*)
...

Answer 2

I would recommend using a recursive CTE to generate all of your 30 min time segments and then JOIN on your table to find the occurrences.
DECLARE #startdate DATETIME = '2016-02-23'--your_starting_date
DECLARE #enddate DATETIME = '2016-03-01' --your_ending_date
;WITH cte AS (
SELECT
#startdate AS start_time
, DATEADD(MINUTE, 30, #startdate) AS end_time
UNION ALL
SELECT DATEADD(MINUTE, 30, start_time) AS start_time
, DATEADD(MINUTE, 30, end_time) AS end_TIME
FROM cte
WHERE end_time <= #enddate
)
SELECT *
INTO #time_table
FROM CTE
OPTION (MAXRECURSION 32727)
GO
SELECT
start_time
, end_time
, SUM(CASE WHEN your_time_column BETWEEN start_time AND end_time THEN 1 ELSE 0 END) AS total_count
FROM #time_table
INNER JOIN your_table --left join if you want all time slots with 0 occurrences
ON your_time_column BETWEEN start_time AND end_time
GROUP BY
start_time
, end_time

Answer 3

This will group by on the hour (not 30 min)
declare #startdatetime datetime = '2016-02-03 00:00:00'
declare #enddatetime datetime = '2016-02-19 23:59:59'
declare #apiserviceid int = 21
select min(usr.STARTDATETIME), max(usr.STARTDATETIME), count(0)
from TABLE 1 usr
where usr.APIREQUESTID = #apiserviceid
and usr.STARTDATETIME >= #startdatetime and usr.STARTDATETIME <= #enddatetime
group by convert(char(13),usr.STARTDATETIME,121)
order by 1;

Answer 4

select cast(year(usr.STARTDATETIME) as varchar)+''
+cast(month(usr.STARTDATETIME) as varchar)+
'-'+cast(day(usr.STARTDATETIME) as varchar)+' '+CAST(DATEPART(HOUR, usr.STARTDATETIME) AS VARCHAR)+':'+
CASE WHEN DATEPART(MINUTE, usr.STARTDATETIME)>30 THEN '31 - '+
CAST((DATEPART(HOUR, usr.STARTDATETIME)+1) AS VARCHAR) +':00' ELSE '00 -
'+CAST(DATEPART(HOUR, usr.STARTDATETIME) AS VARCHAR)+':30' END , COUNT(*)
from TABLE 1 usr
where usr.APIREQUESTID = #apiserviceid
and usr.STARTDATETIME >= #startdatetime and usr.STARTDATETIME <= #enddatetime
group by
cast(year(usr.STARTDATETIME) as varchar)+'-'+
cast(month(usr.STARTDATETIME) as varchar)+'-'+cast(day(usr.STARTDATETIME) as
varchar)+' '+CAST(DATEPART(HOUR, usr.STARTDATETIME) AS VARCHAR)+':'+
CASE WHEN DATEPART(MINUTE, usr.STARTDATETIME)>30 THEN '31 - '+
CAST((DATEPART(HOUR, usr.STARTDATETIME)+1) AS VARCHAR) +':00' ELSE '00 -
'+CAST(DATEPART(HOUR, usr.STARTDATETIME) AS VARCHAR)+':30' END
order by 1;