Grouping, Aggregate, Min, Max

Hi All,

I am not sure how to define with words what I want to accomplish (so can't
ask google the right question :) )

So will try to explain with sample data and expected result:

Scenario 1)

id thing_id category period_id 1 1 A 1 2 1 A 2 3 1 A 3 4 1 A 4 5 1 A
5 6 1 A 6 7 1 A 7 8 1 A 8 9 1 A 9 10 2 A 1 11 2 A 2 12 2 A 3 13 2 A
4

Expected result:

thing_id category periods 1 A 1-9 2 A 1-4
(Sounds easy, group by, thing_id, category use Min and Max for period id -
but further scenarios makes it a bit complicated...)

Scenario 2)

id thing_id category period_id 1 1 A 1 2 1 A 2 3 1 A 3 4 1 A 4 5 1 B 5
6 1 B 6 7 1 B 7 8 1 A 8 9 1 A 9 10 2 A 1 11 2 A 2 12 2 A 3 13 2 A 4
Expected result:
thing_id category periods 1 A 1-4, 8-9 1 B 5-7 2 A 1-4
Scenario 3)

id thing_id category period_id 1 1 A 1 2 1 A 2 3 1 A 3 4 1 A 7 5 1 A 8
6 1 A 9 7 2 A 1 8 2 A 2 9 2 A 3 10 2 A 4
Expected result:

thing_id category periods 1 A 1-3, 7-9 2 A 1-4

So goal is, to group by thing_id, category id - but if period_id is
interupted (not in incremented by 1) to have aggregated spans...

To desired results we have came up using several CTE's (what makes a query
a bit big, and more "procedural way": make cte what calculated diff between
current and previous row, next cte uses previous one to define groupings,
next cte to make aggregates etc...)

So I wonder - is there some kind of aggregate window function what does
desired results?

Many Thanks,

Misa