Subject: Re: Immutable attributes?
From: Robert Treat <xzilla@users.sourceforge.net>
To: Troels Arvin <troels@arvin.dk>
Cc: pgsql-sql@postgresql.org
In-Reply-To: <pan.2003.07.01.09.59.23.580853@arvin.dk>
References: <pan.2003.07.01.09.59.23.580853@arvin.dk>
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Date: 01 Jul 2003 12:28:27 -0400
Message-Id: <1057076907.11365.411.camel@camel>
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On Tue, 2003-07-01 at 05:59, Troels Arvin wrote:
> Hello,
> 
> I have a table like this:
> 
> create table test (
>   "test_id" serial primary key,
>   "created" timestamp with time zone
>      default current_timestamp
>      check(created = current_timestamp),
>   "some_datum" int not null
> );
> 
> My question concerns the "created" attribute: I want this to reflect when
> the tuple was craeated; and I want to make sure that the timestamp is not
> wrong. That will work with the above schema. However, I also want to make
> sure that the "crated" attribut for a tuple is not changed once it has
> been set.
> 
> I'm thinking about implementing it through a trigger, but is there a
> better way to create such "immutable" attributes?
> 

I don't know if it's "better", but this is one of the things people find
the RULE system really handy for. Check the docs, I believe there are
examples of this.

Robert Treat 
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