Michael Fuhr wrote:> On Mon, Sep 26, 2005 at 12:34:59PM +0200, Axel Rau wrote:>>>Am 26.09.2005 um 02:05 schrieb Michael
Fuhr:>>>>>OnFri, Sep 23, 2005 at 09:19:25PM +0200, Axel Rau wrote:>>>>>>>I'm sure this would be the cleanest solution
butremember networks>>>>change.>>>>>>Yes, which is why it's a good idea to automatically propogate those>>>changes to
tablesthat maintain redundant data.>>>>I would not call it redundant but normalized, because network has
some>>attributes,common to all addresses in the net, 1st of all the netmask.>>> An attribute is redundant if it repeats
afact that can be learned> without it. If one table contains IP addresses and another contains> networks, then you can
associateIP addresses and networks with a> join of the two tables; indeed, this is how the "fix the network> column"
updateworks. Having a network column in the address table> simply repeats what could be learned through the join.>>
I agree with Michael here. I think the fundamental problem with your
schema is that it is possible to have contradictory data between the
network and address table, always a bad situation.
I would replace network.id with a serial type value and make the cidr a
separate column, for example:
CREATE TABLE network ( id int not null PRIMARY KEY, address cidr not null, attr1 varchar(10)
null
);
CREATE TABLE address ( id inet PRIMARY KEY, network int NOT NULL REFERENCES network
);
insert into network( id, address, attr1 ) values( 1, '10.1', 'a' );
insert into network( id, address, attr1 ) values( 2, '10.2', 'b' );
go
insert into address( id, network ) values( '10.1.0.1', 1 );
insert into address( id, network ) values( '10.1.0.2', 1 );
insert into address( id, network ) values( '10.1.0.3', 1 );
-- OOPS!
insert into address( id, network ) values( '10.2.0.4', 1 );
go
-- This will "correct" the any addresses put in the wrong network
update address
set network = ( select id from network where address >> address.id )
[additional network stuff snipped]
--
Daryl
"We want great men who, when fortune frowns, will not be discouraged." -- Colonel Henry Knox, 1776
