Question

I have some data as follows (just a few example lines here, tablesize > n thousand entries)

timestamp         duration

2012-09-30T22:00  10800
2012-10-01T08:00   7200
2012-10-01T15:00   3600
2012-10-01T22:00  10800
2012-10-02T07:00   3600
2012-10-02T14:00  18000

and aim to achieve something like:

date               totalDuration

2012-09-30        21600
2012-10-01        32400

and so on.

Durations should be summed up per interval, whereby interval starts at 22:00 each day in this example.
It’s SQL Server 2008.

Answer 1

select 
    cast(dateadd(hour, -22, date) as date), 
    sum(duration) totalDuration
from yourtable
group by cast(dateadd(hour, -22, date) as date)

However, you should note that 2012-09-30T22:00 and2012-10-01T22:00 should not be in the same “time frame day”. 2012-09-30T22:00 and 2012-10-01T21:59 can be in the same day.

Compare this to having thresholds like 1-10 and 10-20. Where does 10 belong to?