Re: query to select a linked list - Mailing list pgsql-sql

From Aaron Bono
Subject Re: query to select a linked list
Date
Msg-id bf05e51c0705090629l7232a6d2we87170b2168c1c82@mail.gmail.com
Whole thread Raw
In response to query to select a linked list  (Louis-David Mitterrand <vindex+lists-pgsql-sql@apartia.org>)
Responses Re: query to select a linked list
List pgsql-sql
On 5/9/07, Louis-David Mitterrand <vindex+lists-pgsql-sql@apartia.org> wrote:
Hi,

To build a threaded forum application I came up the following schema:

forum
------
id_forum | integer| not null  default nextval('forum_id_forum_seq'::regclass)
id_parent| integer|
subject  | text   | not null
message  | text   |

Each message a unique id_forum and an id_parent pointing to the replied
post (empty if first post).

How can I build an elegant query to select all messages in a thread?

Thanks,

Unlike Oracle, PostgreSQL doesn't have anything like a connect by so you would need to write your own stored procedure for that (if new versions of PostgreSQL will have connect by, let me know guys).

What I did was add a little redundancy to my forum tables and had a table structure kind of like this:

forum
   forum_id BIGSERIAL PK,
   name VARCHAR(50)

forum_topic
   forum_topic_id BIGSERIAL PK,
   forum_id BIGINT FK to forum

forum_post
   forum_post_id BIGSERIAL PK,
   create_dt TIMESTAMP,
   subject VARCHAR(255),
   message TEXT,
   forum_topic_id BIGINT FK to forum_topic

and if you want threading, you add a parent_forum_post_id to forum_post (this is where you get the redundancy since only the top forum_post record needs a reference to forum_topic and forum_topic wouldn't even really be needed.

-Aaron
  

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   Aaron Bono
   Aranya Software Technologies, Inc.
   http://www.aranya.com
   http://codeelixir.com
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