SQL for grouping by timeframe with empty frames - php

Question

My goal is it to create a SQL-Query that counts all items in a certain time frame (e.g. 5min)
That's my code so far:
SELECT FROM_UNIXTIME(FLOOR(timestamp_stop/5*60)*(5*60), '%h:%i') AS timekey, timestamp_stop, count(item) AS performance
FROM task
WHERE done = 1
GROUP BY timekey
ORDER BY timestamp_stop ASC
That works great, but doesn't include time frames in which there aren't any records in the database.
I would like to also get these 0-count-ones, up to the current time.
Currently I have no simple/elegant solution in my mind. Any ideas?
Some little post processing in php would also be possible.

Answer 1

As Gordon mentioned, you probably want a secondary table as a basis for ALL 5-minute intervals. I have done similar with a query to self-build using MySQL variables.
select
YourTable.WhateverFields
from
( select
#startTime RangeStart,
#startTime := date_add( #startTime, interval 5 MINUTE ) RangeEnd
from
( select #startTime := '2014-10-20' ) sqlvars,
AnyTableThatHasAsManyDaysYouExpectToReport
limit
12 * numberOfHoursYouNeed * numberOfDaysYouNeed ) DynamicTimeRange
LEFT JOIN YourTable
on YourTable.DateTimeField >= DynamicTimeRange.RangeStart
AND YourTable.DateTimeField < DynamicTimeRange.RangeEnd
So, in this example, the innermost declars a variable "startTime" to Oct 20, 2014 which defaults to 12:00:00. Then the one out from that creates a result set of two columns for a RangeStart and RangeEnd and might look something like...
RangeStart RangeEnd
2014-10-20 00:00 2014-10-20 00:05
2014-10-20 05:00 2014-10-20 00:10
2014-10-20 10:00 2014-10-20 00:15
2014-10-20 05:00 2014-10-20 00:20
2014-10-20 20:00 2014-10-20 00:25
The table reference "AnyTableThatHasAsManyDaysYouExpectToReport" is just that... any table in your database that has at least as many records as you would need to generate your 5-minute intervals for however many hours and days. If you need 1 day worth = 12 records * 5 minutes = 1 hour * 24 hrs = 24*12 = 288 records needed. If you wanted a week, then so be it... multiply that by 7 so my sample just has place-holders to help clarify the intent...
But with the LEFT JOIN, you get all the intervals...

Answer 2

If there are such time frame, but the where clause filters out the records, you can do:
SELECT FROM_UNIXTIME(FLOOR(timestamp_stop/5*60)*(5*60), '%h:%i') AS timekey,
timestamp_stop,
sum(item is not null and done = 1) AS performance
FROM task
GROUP BY timekey
ORDER BY timestamp_stop ASC;
If you still have gaps, then you need to generate a table (or subquery) containing the list of the time frames that you want and use left join.
EDIT:
A subquery is not pleasant. You have to list all the time values. Something like:
SELECT q.timekey, t.timestamp_stop, coalesce(t.performance, 0) as performance
FROM (SELECT '00:00' as timekey UNION ALL
SELECT '00:05' UNION ALL
. . .
) q LEFT JOIN
(SELECT FROM_UNIXTIME(FLOOR(timestamp_stop/5*60)*(5*60), '%h:%i') AS timekey,
timestamp_stop,
COUNT(item) AS performance
FROM task
WHERE done = 1
GROUP BY timekey
) t
ON t.timekey = q.timekey
ORDER BY timestamp_stop ASC;