tackling the building of a complex query - sql

Question

I have intermediate SQL skills, but this is the most complex query I've ever attempted.
My goal is to build a query that will show how many minutes of any given day, a set of 6 drives are in use or idle. Drives that are 'in use' are writing backups to tape aka running a job. A drive can handle only on job at a time. A drive may start and end a job on the same day, or start one day and end 2 days later, if it's a big job. The most important thing is that I be able to report the number of minutes EACH drive is either UP or IDLE (both are important) and also to only report the minutes it worked on the respective day, even if the job carried into the next.
So, complexity results from following
I can't just subtract start time from end time and SUM the elapsed time of all jobs run by a particular drives, because many jobs span midnight, and I must assign the minutes worked to the day in which they occurred. IE. I can't report that a drive performed 50 hours of work in a 24 hour period, just because the end time of the job was 2 days out.
the start time and end time columns are in UTC time, and must be converted to PST.
I need placeholders for minutes of the day when any one of the drive is idle, so that I can show up/idle time for each of the drives.
The tables I need to put together are just two:
a Time calendar table. It has a row for each minute of the day starting with 10-10-2009 through 10-07-2021.
a table containing the start and end times of all jobs that have completed, the names of the drives that ran them, and the names of the jobs.
Here's DDL for a calendar table containing a row for every minute of the day since 2009 through 2014.
WITH e1(min) AS(
SELECT * FROM (VALUES(1),(1),(1),(1),(1),(1),(1),(1),(1),(1))x(n)
),
e2(min) AS(
SELECT e1.min FROM e1, e1 x
),
e4(min) AS(
SELECT e2.min FROM e2, e2 x
),
e8(min) AS(
SELECT e4.min FROM e4, e4 x
),
cteTally(min) AS(
SELECT TOP 6307204 ROW_NUMBER() OVER(ORDER BY (SELECT NULL)) - 1
FROM e8
),
Test(min) AS(
SELECT DATEADD( minute, min, DATEADD( YEAR, -2, GETDATE()))
FROM cteTally)
SELECT DATEADD( MINUTE, DATEDIFF( MINUTE, 0, DATEADD( YEAR, -2, GETDATE())), 0)
FROM Test
WHERE min <= DATEADD( YEAR, 10, GETDATE())
Here’s sample DDL for table containing the device/job/start & end times.
CREATE TABLE JobHistorySummary
(JobName nvarchar(255),
ActualStartTime datetime,
EndTime datetime,
DeviceName nvarchar(128))
INSERT INTO JobHistorySummary
VALUES
('FOAMTools E: Weekly - FULL', '2013-08-04 03:20:00.000', '2013-08-04 20:20:00.000', '1 Drv'),
('HRDuplex D: Weekly - FULL', '2013-08-04 18:26:00.000', '2013-08-05 13:00:00.000', '2 Drv'),
('HRDuplex D: Daily - INC', '2013-08-04 20:44:00.000', '2013-08-05 15:50:00.000', '1 Drv'),
('PayNROLL C: Weekly - FULL', '2013-08-04 00:00:00.000', '2013-08-06 15:40:00.000','3 Drv'),
('PayNROLL C: Daily - INC', '2013-08-05 06:30:00.000', '2013-08-05 06:50:00.000', '4 Drv'),
('SmallIBM F: Daily - FULL', '2013-08-04 00:30:00.000', '2013-08-04 06:30:00.000', '5 Drv'),
('BigIBM F: Daily - INC', '2013-08-06 12:30:00.000', '2013-08-06 12:50:00.000', '6 Drv');
The calculation need to get local time is [ActualStartTime]+ GETDATE() - GETUTCDATE())
Even though I just need two tables, I can't figure out the logic of joining them so that they create NULL placeholders for those datetimes where drives are idle. I would like to count up the rows with NULL values as the idle minutes per drive. Also, I can't figure out how to isolate minutes of usage to the day in which they occurred...meaning no more than 1440 minutes of work per day per drive, even for jobs spanning midnight. Minutes of the next day are allocated as minutes worked by respective drive to the following day.

Answer 1

The following shows how to generate the time in use per day per device. The idle time is just 24 minus that. Assuming you have generated a table with all the dates in the range of the table, lets call that cal with one field dt of type Date. (easy to do). The following gives the general approach.
select devicename, cal.dt, sum(time(least(actualendtime, cal.dt)- time(actualstarttime))
from JobHistorySummary jhs inner join cal
on (jhs.actualstarttime >= cal.dt and jhs.actualendtime < cal.dt)
group by devicename, cal.dt
Now you have use the same statement above using the converted times and also assuming cal is in the converted time zone.
select devicename, cal.dt, sum(time(least(convert_tz(actualendtime,'UTC','US/Pacific'), cal.dt)- time(convert_tz(actualstarttime,'UTC','US/Pacific')))
from JobHistorySummary jhs inner join cal
on (convert_tz(actualstarttime,'UTC','US/Pacific') >= cal.dt and convert_tz(actualendtime,'UTC','US/Pacific') < cal.dt)
group by devicename, cal.dt
But also the above isn't exacty right either because mysql does not do substract and aggregate summing correctly on time values. So you need to use something more like:
select devicename, cal.dt, econd_to_time(sum(time_to_second(timediff(time(least(actualendtime, cal.dt), time(actualstarttime)))))
from JobHistorySummary jhs inner join cal
on (jhs.actualstarttime >= cal.dt and jhs.actualendtime < cal.dt)
group by devicename, cal.dt