Re: (P)SQL for a sum with constraints

Life sure would be easier if that were the case Michal, but no... that
is not the case here. The sum is not a simple sum, it is a sum of all
elements having a lower or equal A and the same C. This is a
"cumulative sum" as pointed out by others.

2009/4/15 Michal Politowski <mpol+pg(at)meep(dot)pl>:
> On Wed, 15 Apr 2009 15:32:42 +0100, Shug Boabby wrote:
>> I simplified my problem a little too much and now I'm stuck trying to
>> use cumulative_sum(). My schema is not only A, B but also has a C
>>
>> A B C
>> 1 0 1
>> 2 1 1
>> 3 0 1
>> 4 2 1
>> 5 1 1
>> 1 0 2
>> 2 1 2
>> 3 0 2
>> 4 2 2
>> 5 1 2
>>
>> and I want to be able to do the cumulative sum only when C is the same. E.g.
>>
>> A funkySumB C
>> 1 0 1
>> 2 1 1
>> 3 1 1
>> 4 3 1
>> 5 4 1
>> 1 0 2
>> 2 1 2
>> 3 1 2
>> 4 3 2
>> 5 4 2
>
> If I understand the problem correctly, why not just something like this?:
>
> SELECT t1.a, sum(t2.b), t1.c FROM abc t1 JOIN abc t2 ON t2.a <= t1.a AND
> t2.c=t1.c GROUP BY t1.a, t1.c;