There is a trick to simplify the thing and avoid using aggregates :
I think it will give you your answer.
Cheers,
Rémi-C
2013/12/13 Misa Simic <misa.simic@xxxxxxxxx>
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
