I have a list of timesheet entries that show a start and stop time. This is sitting in a MySQL database. I need to create bar charts based on this data with the 24 hours of the day along the bottom and the amount of man-hours worked for each hour of the day.
For example, if Alice worked a job from 15:30 to 19:30 and Bob worked from 12:15 to 17:00, the chart would look like this:
I have a WTFey solution right now that involves a spreadsheet going out to column DY or something like that. The needed resolution is 15-minute intervals.
I’m assuming this is something best done in the database then exported for chart creation. Let me know if I’m missing any details. Thanks.
Create a table with just time in it from midnight to midnight containing each minute of the day. In the data warehouse world we would call this a time dimension. Here’s an example:
TIME_DIM -id -time_of_day -interval_15 -interval_30
an example of the data in the table would be
id time_of_day interval_15 interval_30 1 00:00 00:00 00:00 ... 30 00:23 00:15 00:00 ... 100 05:44 05:30 05:30
Then all you have to do is join your table to the time dimension and then group by interval_15. For example:
SELECT b.interval_15, count(*) FROM my_data_table a INNER JOIN time_dim b ON a.time_field = b.time WHERE a.date_field = now() GROUP BY b.interval_15
I came up with a pseudocode solution, hope it helps.
create an array named timetable with 24 entries initialise timetable to zero for each user in SQLtable firsthour = user.firsthour lasthour = user.lasthour firstminutes = 4 - (rounded down integer(user.firstminutes/15)) lastminutes = rounded down integer(user.lastminutes/15) timetable(firsthour) = timetable(firsthour) + firstminutes timetable(lasthour) = timetable(lasthour) + lastminutes for index=firsthour+1 to lasthour-1 timetable(index) = timetable(index) + 4 next index next user
Now the timetable array holds the values you desire in 15 minute granularity, ie. a value of 4 = 1 hour, 5 = 1 hour 15 minutes, 14 = 3 hours 30 minutes.
Here’s another pseudocode solution from a different angle; a bit more intensive because it does 96 queries for every 24hr period:
results =  for time in range(0, 24, .25): amount = mysql("select count(*) from User_Activity_Table where time >= start_time and time <= end_time") results.append(amount)
How about this:
Use that “times” table, but with two columns, containing the 15-minute intervals. The from_times are the 15-minutely times, the to_times are a second before the next from_times. For example 12:30:00 to 12:44:59.
Now get your person work table, which I’ve called “activity” here, with start_time and end_time columns.
I added values for Alice and Bob as per the original question.
Here’s the query from MySQL:
SELECT HOUR(times.from_time) AS 'TIME', count(*) / 4 AS 'HOURS' FROM times JOIN activity ON times.from_time >= activity.start_time AND times.to_time <= activity.end_time GROUP BY HOUR(times.from_time) ORDER BY HOUR(times.from_time)
which gives me this:
TIME HOURS 12 0.7500 13 1.0000 14 1.0000 15 1.5000 16 2.0000 17 1.0000 18 1.0000 19 0.7500
Looks about right…