Splitting time + duration into intervals in t-sql - tsql

Question

Does anyone know of a simple method for solving this?
I have a table which consists of start times for events and the associated durations. I need to be able to split the event durations into thirty minute intervals. So for example if an event starts at 10:45:00 and the duration is 00:17:00 then the returned set should allocate 15 minutes to the 10:30:00 interval and 00:02:00 minutes to the 11:00:00 interval.
I'm sure I can figure out a clumsy approach but would like something a little simpler. This must come up quite often I'd imagine but Google is being unhelpful today.
Thanks,
Steve

Answer 1

You could create a lookup table with just the times (over 24 hours), and join to that table. You would need to rebase the date to that used in the lookup. Then perform a datediff on the upper and lower intervals to work out their durations. Each middle interval would be 30 minutes.
create table #interval_lookup (
from_date datetime,
to_date datetime
)
declare #time datetime
set #time = '00:00:00'
while #time < '2 Jan 1900'
begin
insert into #interval_lookup values (#time, dateadd(minute, 30, #time))
set #time = dateadd(minute, 30, #time)
end
declare #search_from datetime
declare #search_to datetime
set #search_from = '10:45:00'
set #search_to = dateadd(minute, 17, #search_from)
select
from_date as interval,
case
when from_date <= #search_from and
#search_from < to_date and
from_date <= #search_to and
#search_to < to_date
then datediff(minute, #search_from, #search_to)
when from_date <= #search_from and
#search_from < to_date
then datediff(minute, #search_from, to_date)
when from_date <= #search_to and
#search_to < to_date then
datediff(minute, from_date, #search_to)
else 30
end as duration
from
#interval_lookup
where
to_date > #search_from
and from_date <= #search_to

Answer 2

Create TVF that splits single event:
ALTER FUNCTION dbo.TVF_TimeRange_Split_To_Grid
(
#eventStartTime datetime
, #eventDurationMins float
, #intervalMins int
)
RETURNS #retTable table
(
intervalStartTime datetime
,intervalEndTime datetime
,eventDurationInIntervalMins float
)
AS
BEGIN
declare #eventMinuteOfDay int
set #eventMinuteOfDay = datepart(hour,#eventStartTime)*60+datepart(minute,#eventStartTime)
declare #intervalStartMinute int
set #intervalStartMinute = #eventMinuteOfDay - #eventMinuteOfDay % #intervalMins
declare #intervalStartTime datetime
set #intervalStartTime = dateadd(minute,#intervalStartMinute,cast(floor(cast(#eventStartTime as float)) as datetime))
declare #intervalEndTime datetime
set #intervalEndTime = dateadd(minute,#intervalMins,#intervalStartTime)
declare #eventDurationInIntervalMins float
while (#eventDurationMins>0)
begin
set #eventDurationInIntervalMins = cast(#intervalEndTime-#eventStartTime as float)*24*60
if #eventDurationMins<#eventDurationInIntervalMins
set #eventDurationInIntervalMins = #eventDurationMins
insert into #retTable
select #intervalStartTime,#intervalEndTime,#eventDurationInIntervalMins
set #eventDurationMins = #eventDurationMins - #eventDurationInIntervalMins
set #eventStartTime = #intervalEndTime
set #intervalStartTime = #intervalEndTime
set #intervalEndTime = dateadd(minute,#intervalMins,#intervalEndTime)
end
RETURN
END
GO
Test:
select getdate()
select * from dbo.TVF_TimeRange_Split_To_Grid(getdate(),23,30)
Test Result:
2008-10-31 11:28:12.377
intervalStartTime intervalEndTime eventDurationInIntervalMins
----------------------- ----------------------- ---------------------------
2008-10-31 11:00:00.000 2008-10-31 11:30:00.000 1,79372222222222
2008-10-31 11:30:00.000 2008-10-31 12:00:00.000 21,2062777777778
Sample usage:
select input.eventName, result.* from
(
select
'first' as eventName
,cast('2008-10-03 10:45' as datetime) as startTime
,17 as durationMins
union all
select
'second' as eventName
,cast('2008-10-05 11:00' as datetime) as startTime
,17 as durationMins
union all
select
'third' as eventName
,cast('2008-10-05 12:00' as datetime) as startTime
,100 as durationMins
) input
cross apply dbo.TVF_TimeRange_Split_To_Grid(input.startTime,input.durationMins,30) result
Sample usage result:
eventName intervalStartTime intervalEndTime eventDurationInIntervalMins
--------- ----------------------- ----------------------- ---------------------------
first 2008-10-03 10:30:00.000 2008-10-03 11:00:00.000 15
first 2008-10-03 11:00:00.000 2008-10-03 11:30:00.000 2
second 2008-10-05 11:00:00.000 2008-10-05 11:30:00.000 17
third 2008-10-05 12:00:00.000 2008-10-05 12:30:00.000 30
third 2008-10-05 12:30:00.000 2008-10-05 13:00:00.000 30
third 2008-10-05 13:00:00.000 2008-10-05 13:30:00.000 30
third 2008-10-05 13:30:00.000 2008-10-05 14:00:00.000 10
(7 row(s) affected)