Re: (P)SQL for a sum with constraints

Michal... I must apologise, your suggestion worked a treat!!!

I never realised it was possible to do a join on a table to itself before!

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;
>
> --
> Michał Politowski
> Talking has been known to lead to communication if practiced carelessly.
>
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