How to count every half hour? - sql

Question

I have a query that its counting every hour, using a pivot table.
How would it be possible to get the count for every 30 minutes?
for example 8:00-8:29,8:30-8:59,9:00-9:29 etc. until 5:00
SELECT CONVERT(varchar(8),start_date,1) AS 'Day',
SUM(CASE WHEN DATEPART(hour,start_date) = 8 THEN 1 ELSE 0 END) as eight ,
SUM(CASE WHEN DATEPART(hour,start_date) = 9 THEN 1 ELSE 0 END) AS nine,
SUM(CASE WHEN DATEPART(hour,start_date) = 10 THEN 1 ELSE 0 END) AS ten,
SUM(CASE WHEN DATEPART(hour,start_date) = 11 THEN 1 ELSE 0 END) AS eleven,
SUM(CASE WHEN DATEPART(hour,start_date) = 12 THEN 1 ELSE 0 END) AS twelve,
SUM(CASE WHEN DATEPART(hour,start_date) = 13 THEN 1 ELSE 0 END) AS one_clock,
SUM(CASE WHEN DATEPART(hour,start_date) = 14 THEN 1 ELSE 0 END) AS two_clock,
SUM(CASE WHEN DATEPART(hour,start_date) = 15 THEN 1 ELSE 0 END) AS three_clock,
SUM(CASE WHEN DATEPART(hour,start_date) = 16 THEN 1 ELSE 0 END) AS four_clock
FROM test
where user_id is not null
GROUP BY CONVERT(varchar(8),start_date,1)
ORDER BY CONVERT(varchar(8),start_date,1)
I use sql server 2012 (version Microsoft SQL Server Management Studio 11.0.3128.0)

Answer 1

Try using iif as below:
SELECT CONVERT(varchar(8),start_date,1) AS 'Day', SUM(iif(DATEPART(hour,start_date) = 8 and
DATEPART(minute,start_date) >= 0 and
DATEPART(minute,start_date) =< 29,1,0)) as eight_tirty
FROM test where user_id is not null GROUP BY
CONVERT(varchar(8),start_date,1) ORDER BY
CONVERT(varchar(8),start_date,1)

Answer 2

To get counts by day and half hour, something like this should work.
SELECT day, half_hour, count(1) AS half_hour_count
FROM (
SELECT
CAST(start_date AS date) AS day,
DATEPART(hh, start_date)
+ 0.5*(DATEPART(n,start_date)/30) AS half_hour
FROM test
WHERE user_id IS NOT NULL
) qry
GROUP BY day, half_hour
ORDER BY day, half_hour;
Formatting the result could be done later.

Answer 3

You need a few things, and then this query just falls together.
First, assuming you need multiple dates, you're going to want what's known as a Calendar Table (hands down, probably the most useful analysis table).
Next, you're going to want either an existing Numbers table if you have one, or just generate the first on the fly:
WITH Halfs AS (SELECT CAST(0 AS INT) m
UNION ALL
SELECT m + 1
FROM Halfs
WHERE m < 24 * 2)
SELECT m
FROM Halfs
(recursive CTE - generates a table with a list of numbers starting at 0).
These two tables will provide the basis for a range query based on the timestamps in your main table. This will make it very easy for the optimizer to bucket rows for whatever aggregation you're doing. That's done by CROSS JOINing the two tables together in a subquery, as well as adding a couple of other derived columns:
WITH Halfs AS (SELECT CAST(0 AS INT) m
UNION ALL
SELECT m + 1
FROM Halfs
WHERE m < 24 * 2)
SELECT calendarDate, m, rangeStart, rangeEnd
FROM (SELECT Calendar.calendarDate, Halfs.m rangeGroup,
DATEADD(minutes, m * 30, CAST(Calendar.calendarDate AS DATETIME2) rangeStart,
DATEADD(minutes, (m + 1) * 30, CAST(Calendar.calendarDate AS DATETIME2) rangeEnd
FROM Calendar
CROSS JOIN Halfs
WHERE Calendar.calendarDate >= CAST('20160823' AS DATE)
AND Calendar.calendarDate < CAST('20160830' AS DATE)
-- OR whatever your date range actually is.
) Range
ORDER BY rangeStart
(note that, if the range of dates is sufficiently large, it may be beneficial to save this off as a temporary table with indicies. For small tables and datasets, the performance gain isn't likely to be noticeable)
Now that we have our ranges, it's trivial to get our groups, and pivot the table.
Oh, and SQL Server has a specific operator for PIVOTing.
WITH Halfs AS (SELECT CAST(0 AS INT) m
UNION ALL
SELECT m + 1
FROM Halfs
WHERE m < 3 * 2)
-- Intentionally limiting range for example only
SELECT calendarDate AS day, [0], [1], [2], [3], [4], [5], [6]
-- If you're displaying "nice" names,
-- do it at this point, or in the reporting application
FROM (SELECT Range.calendarDate, Range.rangeGroup
FROM (SELECT Calendar.calendarDate, Halfs.m rangeGroup,
DATEADD(minutes, m * 30, CAST(Calendar.calendarDate AS DATETIME2) rangeStart,
DATEADD(minutes, (m + 1) * 30, CAST(Calendar.calendarDate AS DATETIME2) rangeEnd
FROM Calendar
CROSS JOIN Halfs
WHERE Calendar.calendarDate >= CAST('20160823' AS DATE)
AND Calendar.calendarDate < CAST('20160830' AS DATE)
-- OR whatever your date range actually is.
) Range
LEFT JOIN Test
ON Test.user_id IS NOT NULL
AND Test.start_date >= Range.rangeStart
AND Test.start_date < Range.rangeEnd
) AS DataTable
PIVOT (COUNT(*)
FOR Range.rangeGroup IN ([0], [1], [2], [3], [4], [5], [6])) AS PT
-- Only covers the first 6 groups,
-- or the first three hours.
ORDER BY day
The pivot should take care of the getting individual columns, and COUNT will automatically resolve null rows. Should be all you need.