From: "Ray Madigan" <ray@madigans.org>
To: "Pgsql-Sql" <pgsql-sql@postgresql.org>
Subject: Re: LinkedList
Date: Wed, 26 Apr 2006 10:35:15 -0700
Message-ID: <IEELLOAPJFACBDBGELGHAELAEDAA.ray@madigans.org>
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Scott,

Thanks for your reply,  I tried what you said, worked around a few things
but I am still stuck.  The main reason is I didn't do an adequate job of
explaining the situation.  The table implements many linked lists and I want
to traverse one of them given the end of the list.

Say the table contains

h | v | j
1   0   100
3   1   300
5   3   500
7   5   700

2   0   200
4   2   400
6   4   600
8   6   800

If I specify t.h = 8 I want to traverse the even part of the table
If I specify t.h = 7 I want to traverse the odd part of the table

If you can send me to a book to read I am willing

Thanks

-----Original Message-----
From: pgsql-sql-owner@postgresql.org
[mailto:pgsql-sql-owner@postgresql.org]On Behalf Of Scott Marlowe
Sent: Wednesday, April 26, 2006 8:59 AM
To: Ray Madigan
Cc: pgsql-sql@postgresql.org
Subject: Re: [SQL] LinkedList


On Wed, 2006-04-26 at 11:09, Ray Madigan wrote:
> 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:
>
> 1, 0
> 3, 1
> 7, 3
> 9, 7
> ...
>
> Any suggestions would be helpful, or I will have to implement the table
> differently.

You should be able to do this with a fairly simple self-join...

select a.id, b.aid, a.field1, b.field1
from mytable a
join mytable b
on (a.id=b.aid)

Or something like that.

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