Date: Thu, 27 Apr 2006 22:58:26 -0500 (CDT)
From: "Ben K." <bkim@coe.tamu.edu>
To: pgsql-sql@postgresql.org
cc: Ray Madigan <ray@madigans.org>
Subject: Re: LinkedList
In-Reply-To: <1146067158.23538.264.camel@state.g2switchworks.com>
Message-ID: <Pine.GSO.4.64.0604272249570.3093@coe.tamu.edu>
References: <IEELLOAPJFACBDBGELGHIEKMEDAA.ray@madigans.org>
	<1146067158.23538.264.camel@state.g2switchworks.com>
MIME-Version: 1.0
Content-Type: TEXT/PLAIN; charset=US-ASCII; format=flowed

> I have a table that I created that implements a linked list.  I am not an
> expert SQL developer and was wondering if there are known ways to traverse
> the linked lists.  Any information that can point me in the direction to
> figure this out would be appreciated.  The table contains many linked lists
> based upon the head of the list and I need to extract all of the nodes that
> make up a list.  The lists are simple with a item and a link to the history
> item so it goes kind of like:

It may not be exactly suitable, but this one does only traversal (assuming 
the list is not clsoed)

create table linkedlist(prevnode int, nextnode int, val int);
-- HEAD
insert into linkedlist values(null,1,0);
insert into linkedlist values(1,2,10);
insert into linkedlist values(2,3,20);
insert into linkedlist values(3,4,30);
insert into linkedlist values(4,5,40);
-- TAIL
insert into linkedlist values(5,null,50);

-- TRAVERSE
begin;
declare mc cursor for select * from linkedlist order by nextnode;
fetch 1 from mc;
fetch 1 from mc;
...
close mc;
commit;

which is nothing more than,
select * from linkedlist order by nextnode;


Regards,

Ben K.
Developer
http://benix.tamu.edu