Question

I have a table(begin, end, typeid) with time intervals, something like this:

...
14:10:44    14:15:51  1
14:12:33    14:18:42  2
15:24:09    15:24:17  1
...

There is some rules: intervals with type id 2 intersepts with intervals of type 1.
And after processing I get something like this:

...
14:10:44    14:18:42 <-- as a result of merging
15:24:09    15:24:17 
...

Is there exists any tehnics or methods to work with such data? May be there exists any usefull representation of intervals of time?

P.S. SQL Server 2008 R2

Answer 1

It is really hard to code up against data like yours. I have seen it a couple of times in real life situations. Here are 2 ideas.

declare @t table(low time, high time, type_id tinyint)

insert @t values('14:10:44','14:15:51', 1)
insert @t values('14:12:33','14:18:42', 2)
insert @t values('15:24:09','15:24:17', 1)

select low, coalesce(a.high, t.high) high 
from @t t 
cross apply (select min(high) high 
from @t t2 
where high > t.high and type_id = 2  
and not exists (select 1 from @t 
where t2.high between low and high and type_id = 2 and not 
(t2.high = high and t2.low = low))) a
where type_id = 1

Here is an alternative way. May even be better, depending on your data.

;with cte as 
(
select low low2, high, low 
from @t where type_id = 1 
union all
select cte.high, t.high, cte.low
from @t t 
join cte on cte.high > t.low 
and cte.high < t.high 
where t.type_id = 2
)
select low, max(high) high  from cte group by low

I am assuming that the low with type_id 1 is always the lowest in the set. I am also assuming there are no overlapping sets for rows with type_id 1 (and their subrows) since that would make no sense at all.