Number of rows per hour starting at a specific time - sql

Question

In order to get data for some reporting, I have to know how much lines have been inserted per hour in a table starting at a specific hour for a specific day. I already found a part of the solution in another question but I didn't manage to find a way to adapt it in my case. This is the code I've written so far:
SELECT DATEADD(HOUR, DATEDIFF(HOUR, 0, t.mydatetime), 0) AS HOUR_CONCERNED,
COUNT(*) AS NB_ROWS
FROM mytable t
WHERE CONVERT(DATETIME, FLOOR(CONVERT(FLOAT, t.mydatetime))) = '2016-06-06'
GROUP BY DATEADD(HOUR, DATEDIFF(HOUR, 0, t.mydatetime), 0)
ORDER BY HOUR_CONCERNED;
It gives me the following results:
HOUR_CONCERNED NB_ROWS
------------------- --------
2016-06-06 10:00:00 2157
2016-06-06 11:00:00 60740
2016-06-06 12:00:00 66189
2016-06-06 13:00:00 77096
2016-06-06 14:00:00 90039
The problem is that I can't find a way to start my results at a specific time such as 9.30am and to get the number of rows per hour starting from this time. In other words, I'm looking for the number of rows between 9.30am and 10.30am, between 10.30am and 11.30am, etc. The results I'm looking for should look like this:
HOUR_CONCERNED NB_ROWS
------------------- --------
2016-06-06 09:30:00 3550
2016-06-06 10:30:00 33002
2016-06-06 11:30:00 42058
2016-06-06 12:30:00 55008
2016-06-06 13:30:00 72000
Is there an easy way to adapt my query and get those results ?

Answer 1

Given a specific starting time, you can get hour blocks by finding the number of minutes since your start time, and dividing by 60, then adding this number of hours back to the start time e.g.
DECLARE #StartTime DATETIME2(0) = '20160606 09:30';
WITH DummyData (mydatetime) AS
( SELECT TOP 200 DATEADD(MINUTE, ROW_NUMBER() OVER(ORDER BY [object_id]) - 1, #StartTime)
FROM sys.all_objects
)
SELECT HoursSinceStart = FLOOR(DATEDIFF(MINUTE, #StartTime, mydatetime) / 60.0),
Display = DATEADD(HOUR, FLOOR(DATEDIFF(MINUTE, #StartTime, mydatetime) / 60.0), #StartTime),
Records = COUNT(*)
FROM DummyData
WHERE myDateTime >= #StartTime
GROUP BY FLOOR(DATEDIFF(MINUTE, #StartTime, mydatetime) / 60.0)
ORDER BY Display;
Which gives:
HoursSinceStart Display Records
0 2016-06-06 09:30:00 60
1 2016-06-06 10:30:00 40
2 2016-06-06 11:30:00 60
3 2016-06-06 12:30:00 20
I have left the HoursSinceStart column in, to hopefully assist in deconstructing the logic contained in the Display column
The problem with this method is that it will only give you results for blocks that exist, if you also need those that don't you will need to generate all time blocks using a numbers table, then left join to your data:
You can quickly generate a series of numbers using this:
DECLARE #StartTime DATETIME2(0) = '20160606 09:30';
-- GENERATE 10 ROWS
WITH N1 AS (SELECT N FROM (VALUES (1),(1),(1),(1),(1),(1),(1),(1),(1),(1)) n (N)),
-- CROSS JOIN THE 10 ROWS TO GET 100 ROWS
N2 (N) AS (SELECT 1 FROM N1 AS N1 CROSS JOIN N1 AS N2),
--CROSS JOIN THE 100 ROWS TO GET 10,000 ROWS
N3 (N) AS (SELECT 1 FROM N2 AS N1 CROSS JOIN N2 AS N2),
--APPLY ROW_NUMBER TO GET A SET OF NUMBERS FROM 0 - 99,999
Numbers (N) AS (SELECT ROW_NUMBER() OVER(ORDER BY N) - 1 FROM N3)
SELECT *,
TimeStart = DATEADD(HOUR, N, #StartTime),
TimeEnd = DATEADD(HOUR, N + 1, #StartTime)
FROM Numbers;
Which gives something like:
N TimeStart TimeEnd
--------------------------------------------------
0 2016-06-06 09:30:00 2016-06-06 10:30:00
1 2016-06-06 10:30:00 2016-06-06 11:30:00
2 2016-06-06 11:30:00 2016-06-06 12:30:00
3 2016-06-06 12:30:00 2016-06-06 13:30:00
4 2016-06-06 13:30:00 2016-06-06 14:30:00
5 2016-06-06 14:30:00 2016-06-06 15:30:00
6 2016-06-06 15:30:00 2016-06-06 16:30:00
7 2016-06-06 16:30:00 2016-06-06 17:30:00
Then you can left join your data to this (you will probably need an end time too);
DECLARE #StartTime DATETIME2(0) = '20160606 09:30',
#EndTime DATETIME2(0) = '20160606 15:30';
WITH DummyData (mydatetime) AS
( SELECT TOP 200 DATEADD(MINUTE, ROW_NUMBER() OVER(ORDER BY [object_id]) - 1, #StartTime)
FROM sys.all_objects
),
-- GENERATE NUMBERS
N1 AS (SELECT N FROM (VALUES (1),(1),(1),(1),(1),(1),(1),(1),(1),(1)) n (N)),
N2 (N) AS (SELECT 1 FROM N1 AS N1 CROSS JOIN N1 AS N2),
N3 (N) AS (SELECT 1 FROM N2 AS N1 CROSS JOIN N2 AS N2),
Numbers (N) AS (SELECT ROW_NUMBER() OVER(ORDER BY N) - 1 FROM N3),
TimePeriods AS
( SELECT TimeStart = DATEADD(HOUR, N, #StartTime),
TimeEnd = DATEADD(HOUR, N + 1, #StartTime)
FROM Numbers
WHERE DATEADD(HOUR, N, #StartTime) < #EndTime
)
SELECT tp.TimeStart, tp.TimeEnd, Records = COUNT(dd.myDateTime)
FROM TimePeriods AS tp
LEFT JOIN DummyData AS dd
ON dd.mydatetime >= tp.TimeStart
AND dd.mydatetime < tp.TimeEnd
GROUP BY tp.TimeStart, tp.TimeEnd
ORDER BY tp.TimeStart;
Which will return 0 where there are no records:
TimeStart TimeEnd Records
---------------------------------------------------------
2016-06-06 09:30:00 2016-06-06 10:30:00 60
2016-06-06 10:30:00 2016-06-06 11:30:00 60
2016-06-06 11:30:00 2016-06-06 12:30:00 60
2016-06-06 12:30:00 2016-06-06 13:30:00 20
2016-06-06 13:30:00 2016-06-06 14:30:00 0
2016-06-06 14:30:00 2016-06-06 15:30:00 0

Answer 2

Try this:
SELECT DATEADD( MINUTE, 30, DATEADD(HOUR, DATEDIFF(HOUR, 0, DATEADD( MINUTE, -30, t.mydatetime)), 0)) AS HOUR_CONCERNED,
COUNT(*) AS NB_ROWS
FROM mytable t
WHERE CONVERT(DATETIME, FLOOR(CONVERT(FLOAT, t.mydatetime))) = '2016-06-06'
GROUP BY DATEADD(HOUR, DATEDIFF(HOUR, 0, DATEADD( MINUTE, -30, t.mydatetime)), 0)
ORDER BY HOUR_CONCERNED;
I added a 30 min offset into the GROUP BY function to treat 9:30 as 9:00, 10:30 as 10:00 and so on. In the select part I reverse this offset to give a proper interval.
The WHERE condition in your query needs to change though for performance reasons. Instead of truncating timestamps to a nearest day, you should filter by a range:
WHERE t.mydatetime >= CONVERT( DATETIME, '2016-06-06' ) AND t.mydatetime < CONVERT( DATETIME, '2016-06-07' )

Answer 3

You need to have the time in the where clause, and set a greater than against the time you want to measure from? Also, you can use DATEPART to get the hours.
SELECT NB_ROWS = COUNT(*)
,HOUR_CONCERNED = DATEPART(HOUR, InsertedDate)
FROM table
WHERE InsertedDate = '20160531'
AND InsertedDate> time
GROUP BY DATEPART(HOUR, InsertedDate)