Re: How to obtain algebraic sum of equal lines

Hi Frank,
* Frank Bax <fbax(at)sympatico(dot)ca> [250406, 17:25]:
> At 05:21 PM 4/25/06, Ennio-Sr wrote:
>
> >Hi Oisin and Frank,
> >
> >* Frank Bax <fbax(at)sympatico(dot)ca> [250406, 16:41]:
> >> At 04:12 PM 4/25/06, Ennio-Sr wrote:
> >>
> >> >Hi all,
> >> >Is it possible, given the following table:
> >> >
> >> >cod_rif | titolo | quantity | cmf | u_qq | mont | vend | sum
> >>
> >>---------+--------+----------+---------+--------+---------+------+-------
> >> > 26 | aaa | -1000 | 6.11098 | 6.176 | 6.1110 | t | -1000
> >> > 7 | aaa | 2500 | 25.455 | 0 | 60.0897 | f | 2500
> >> > 28 | bbb | 2700 | 3.862 | 4.6 | 4.1957 | f | 2700
> >> > 3 | bbb | 500 | 6.057 | 10.129 | 18.7311 | f | 500
> >> > 34 | bbb | -700 | 0 | 0 | 0.0000 | t | -700
> >> > 6 | bbb | -500 | 2.703 | 4.757 | 3.7151 | f | -500
> >> > 30 | ccc | 5000 | 1.717 | 1.489 | 1.7170 | f | 5000
> >> > 33 | ccc | 10000 | 4.36 | 0 | 4.3600 | f | 10000
> >> > 11 | ddd | -1500 | 10.537 | 4.021 | 20.5815 | t | -1500
> >> > 32 | ddd | 1500 | 0.55896 | 1.119 | 0.5590 | f | 1500
> >> >(10 rows)
> >> >
> >> >to get a selection whereby the algebraic sum of "quantity" for each
> >equal
> >> >'titolo'
> >> >is returned?
> >> >
..............
> >
> >The point is that command would return two cols only, whereas I would
> >like to have all the cols, like:
> >
> > 26 | aaa | 1500 | 6.11098 | 6.176 | 6.1110 | t | 1500
> > 28 | bbb | 2000 | 3.862 | 4.6 | 4.1957 | f | 3200
> >
> >i.e. aaa=(-1000+2500=1500), bbb=(2700+500-700-500)=2000
> >which, I fear, is not possible ;-(
>
>
> It might be possible, but only if you can provide a rule for choosing
> values for the other columns. For example, when titolo='aaa', then cod_rif
> could be 26 or 7; you chose 26 for your sample output - why is 7 not the
> "right" result for this column.
>

The problem, as I see it, is that each line for the same titolo has
many different values (not only cod_rif, but also other cols differs)
and (probably) PG doesn't know how to sum 'potatoes'+'tomatoes'...
I think I could drop cod_ref in the select, if that helped, not the
other columns.

Oisin's suggestion helps a bit, however.
Thanks,
Ennio

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