Overlapping Date Ranges - Identifying Only the Overlap

Question

I\'ve seen a lot of solutions to identify records where date ranges overlap, and still other examples of merging overlapping ranges.

However I am interested in results

Answer 1

Here's the answer:

select t.customerid, t.eff_dt, count(distinct t2.productId),
       MIN(t2.end_dt) as end_dt
from #tmp t join
     #tmp t2
     on t.CustomerID = t2.CustomerID and
        t.Eff_Dt between t2.Eff_Dt and t2.End_Dt
group by t.CustomerID, t.eff_dt
having count(distinct t2.productId) = 3

This is using a self-join to count the number of different products on each eff_dt. You want three distinct products, so that is what the having clause is doing.

There are three distinct products until one of them ends. That would be the first end_dt after the effective date -- which is calculated by the min(end_dt).