Re: Combine query views into one SQL string

From: "Gledatelj" <barney(at)yahoo(dot)com>
To: pgsql-sql(at)postgresql(dot)org
Subject: Re: Combine query views into one SQL string
Date: 2001-09-11 06:33:30
Message-ID: 9nkbg3$9db$1@bagan.srce.hr
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Hy Maik,

you can select it directly from the tables using following sql statement
(but it's same as using views):

select
t1.id, t1.f1, t2.f2
from
(select id, sum(amount) f1
from table1
group by id) t1,
(select id, sum(amount) f2
from table2
group by id) t2
where
t1.id = t2.id

but, you must also know that in this way you may not get all the records
(sum of amount of all id-s) if this is your intention, but just sum of
amount of identical id-s (contained in both tables).

Maybe this will help you.

"Eimas" <eimas(at)lycos(dot)com> wrote in message
news:63e57aa8(dot)0109091520(dot)4f975abd(at)posting(dot)google(dot)com(dot)(dot)(dot)
> "Maik" <K(dot)Maik(at)web(dot)de> wrote in message
news:<9na15r$ku4$1(at)narses(dot)hrz(dot)tu-chemnitz(dot)de>...
> > Its clear, union concat the two results.
> >
> > But he can also use this join version, if its the intention.
> >
> > select t1.id, sum(t1.amount), t2.id, sum(t2.amount) from table1 as t1,
> > table2 as t2 where t1.id=t2.id;
> >
> > Ciao Maik
>
> This is not right, i wouldnt even bather you if this was the simple
> answer.
>
> t1.id=t2.id would mean in doubled or tripled aggregation,
> since t1.id and t2.id are not unique, thats why I had to aggregate
> them in first Q1, Q2 querires, and link them by ID in the last one.
>
> I don't understand what UNION got to do here. then you probably have
> to make three union links of inner, left and right joined tables.
>
> This is not that easy as it seems.
> Is there a universal SQL string "expanding" rules, like in math or so?
>
> Thanks

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