From: A. Kretschmer <andreas.kretschmer@schollglas.com>
To: pgsql-novice@postgresql.org
To: pgsql-sql@postgresql.org
Subject: Re: [SQL] Select last there dates
Date: Thu, 21 Jun 2007 15:24:40 +0200
Message-ID: <20070621132440.GM1405@a-kretschmer.de> (raw)
In-Reply-To: <1c23c8e70706210600he74293ci83bdbc557ee2dba8@mail.gmail.com>
References: <1c23c8e70706210118h6b9490e3s11e2a6ba15cdff6c@mail.gmail.com>
<20070621095025.GG1405@a-kretschmer.de>
<1c23c8e70706210600he74293ci83bdbc557ee2dba8@mail.gmail.com>
am Thu, dem 21.06.2007, um 16:00:05 +0300 mailte Loredana Curugiu folgendes:
> So Andreas, would you please give some more explanations
> on your solution? I didn't work with functions and aggregate till
> now.
I will try it, but i'm not a nativ english speaker and thats why i have
some problems...
>
> I don't understand how this comma_aggregate works. I can see that this
> function it is defined with two arguments, but the aggredate it is called
> with a single argument.
An aggregate needs among others a so called 'SFUNC' with 2 parameters:
internal-state and next data item. It returns the next-internal-state.
This is explained here:
http://www.postgresql.org/docs/8.1/interactive/sql-createaggregate.html>
> And what is LANGUAGE sql IMMUTABLE STRICT ?
An IMMUTABLE function can't modify the database
http://www.postgresql.org/docs/current/static/xfunc-volatility.html
STRICT:
http://www.postgresql.org/docs/8.2/static/xfunc-c.html
,----[ ]
| Notice that we have specified the functions as "strict", meaning that
| the system should automatically assume a null result if any input value
| is null.
`----
Andreas
--
Andreas Kretschmer
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To: pgsql-sql@postgresql.org
Cc: andreas.kretschmer@schollglas.com, pgsql-novice@postgresql.org
Subject: Re: [SQL] Select last there dates
In-Reply-To: <20070621132440.GM1405@a-kretschmer.de>
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