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Re: Query question, subselects and referencing out?

From: Andreas Seltenreich <andreas+pg(at)gate450(dot)dyndns(dot)org>
To: Jan Danielsson <jan(dot)danielsson(at)gmail(dot)com>
Cc: pgsql-novice(at)postgresql(dot)org
Subject: Re: Query question, subselects and referencing out?
Date: 2006-02-18 11:04:19
Message-ID: 87k6btq66k.fsf@gate450.dyndns.org (view raw or flat)
Thread:
Lists: pgsql-novice
Jan Danielsson writes:

> I have managed to put this together:
>
> select from_ip, count(from_ip) as entries, max(ts)::timestamp(0) as
> last_access from log where to_port=22 and direction='in' group by from_ip
>
>    So the only thing I'm missing is the total number of log entries, but
> that's where I'm stuck. My instinct is to try to use subqueries:
>
> select from_ip, count(from_ip) as entries, count(select * from log where
> ...) as tot_entries, max(ts)::timestamp(0) as last_access from log where
> to_port=22 and direction='in' group by from_ip
>
> ..but how do I match the from_ip in the inner select with the outer one?

I guess that is the point when you're supposed to give table an alias:

| select from_ip, count(from_ip) as entries, (select count(*) from log where

from_ip = outerlog.from_ip

| ) as tot_entries, max(ts)::timestamp(0) as last_access from log

as outerlog

| where to_port=22 and direction='in' group by from_ip

Also note the moved aggregate in the subquery.

regards,
Andreas
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