Query to calculate partial labor hours - sql

Question

I'm not sure if it's possible to do exactly what I'm wanting, but hopefuly someone here can give me some direction. I'm trying to do some labor reports and a few of them require me to make comparisons to labor by hour.
Starting as simple as possible, I would like to know how I could query over employee In and Out times for a given hour and find out how many total hours have been worked.
For example, if I have:
id In Out
-- ------- ------
1 12:00pm 8:30pm
2 12:00pm 8:15pm
3 8:15pm 11:00pm
and I wanted to query for how many hours of labor there were in the 8 o'clock hour then I would expect to see a result of 2 hours (or 120 minutes... 30m + 15m + 45m).
Then moving on from there I'd like to write a query that will show this information for the whole day, but group on the hour showing this same information for each hour. I realize there are other concerns (i.e. I would also need to group on the date, etc.) but if I can figure this out then the rest will be a breeze.
For more context, you can see a similar question I have here: Query for labor cost by hour
(The difference between this question and the other one, if it's not clear, is that I am asking about a specific approach here. If you think you have a better approach to this problem, then please add it to the other question.)

Answer 1

Try this to get your started, need to tweak it a bit, but should give you what you want on your sample data...
select id,
minutes - case when inMinutes < 0 then 0 else inminutes end as TotalMins
from
(
select id,
case when datediff(mi,'8:00pm',OutTime) >60 then 60 else datediff(mi,'8:00pm',OutTime) end as Minutes,
case when datediff(mi,'8:00pm',InTime) >60 then 60 else datediff(mi,'8:00pm',InTime) end as InMinutes
from testhours
) xx

Answer 2

If that is a Microsoft system then datetime values can be converted to double precision floating point numbers where the decimal point divides the date and time like this:
integer part: number of days since 1900-01-01
decimal part: time in the day (so that 0.5 = 12:00:00)
So you could use something like this:
-- sample datetime values
declare #in datetime, #out datetime
set #in = '2012-01-18 12:00:00'
set #out = '2012-01-18 20:30:00'
-- calculation
declare #r_in real, #r_out real
set #r_in = cast(#in as real)
set #r_out = cast(#out as real)
select (24 * (#r_out - #r_in)) as [hours]
BUT it is not that precise, so I would recommend this for calculation:
select cast(datediff(second, #in, #out) as real)/3600 as [hours]

Answer 3

OK, I would also suggest to use functions because that's maybe a lot slower on large tables but also easier and more simple to code.
But here's another solution without functions:
-- the day you're interested in:
declare #day datetime
set #day = '2012-01-20'
-- sample data
declare #moves table (id int, tin datetime, tout datetime)
insert into #moves values
(1, '2012-01-20 06:30:00', '2012-01-20 15:45:00'),
(2, '2012-01-20 13:05:00', '2012-01-20 19:45:00'),
(3, '2012-01-20 10:10:00', '2012-01-20 10:50:00'),
(4, '2012-01-20 19:35:00', '2012-01-20 21:00:00')
-- a helper table with hours
declare #i int
declare #hours table (h int, f datetime, t datetime)
set #i = 0
while #i < 24
begin
insert into #hours values(#i, dateadd(hour, #i, #day), dateadd(hour, #i + 1, #day))
set #i = #i + 1
end
-- here's the code
select h.h,
sum(case sign(datediff(second, h.f, m.tin))
when 1 then
case sign(datediff(second, m.tout, h.t))
when 1 then datediff(minute, m.tin , m.tout)
else datediff(minute, m.tin , h.t)
end
when null then null
else
case sign(datediff(second, m.tout, h.t))
when 1 then datediff(minute, h.f, m.tout)
else datediff(minute, h.f, h.t)
end
end) as minutesWorked,
count(distinct m.id) as peopleWorking
from #hours h inner join #moves m
-- on h.f >= m.tin and h.t <= m.tout
on h.f <= m.tout and h.t >= m.tin
group by h.h
order by h.h
This will give you the following results:
h minutesWorked peopleWorking
----------- ------------- -------------
6 30 1
7 60 1
8 60 1
9 60 1
10 100 2
11 60 1
12 60 1
13 115 2
14 120 2
15 105 2
16 60 1
17 60 1
18 60 1
19 70 2
20 60 1
21 0 1