Postgres Pro
Downloads
Home   >   mailing lists

Thread: Chain/Thread Problem

Chain/Thread Problem

From
sammynash@uboot.com (Sammy)
Date:
Hi, 

I have a SQL problem for you all. What SQL qurey would I have to make
on the following table to extract the chain (thread) of emails in a
conversation.

        id|emailid|referenceid        -----------------------         1|  e125 |   Null             (Start of chain)
    2|  r1fe |   e125             (2nd letter in chain)         ...         ...         n|  e4ju |   r1fe
(3rdin chain)
 

ie
a sucessulf qurey would return rows 1,2 & n because they are all in
the chain.

Hope you can help me with my problem,

Re: Chain/Thread Problem

From
"J Sensel"
Date:
Sammy..

A quick and dirty approach is something like this:

id|threadid|emailid|referenceid|pathlevel
---------------------------------------
1|t101|e323|null|0
2|t101|e545|e323|1
3|t101|e822|e545|2
4|t101|e999|e323|1
etc..

Do the sorting when you insert the records.  Then they can be quickly &
easily retrieved.  Otherwise you're looking at a recursive query.  Not very
efficient.  This way is crude but allows the engine to optimize queries with
indexes.

HTH

Jim


"Sammy" <sammynash@uboot.com> wrote in message
news:6729af8d.0305160646.d9ab2d2@posting.google.com...
> Hi,
>
> I have a SQL problem for you all. What SQL qurey would I have to make
> on the following table to extract the chain (thread) of emails in a
> conversation.
>
>
>          id|emailid|referenceid
>          -----------------------
>           1|  e125 |   Null             (Start of chain)
>           2|  r1fe |   e125             (2nd letter in chain)
>           ...
>           ...
>           n|  e4ju |   r1fe             (3rd in chain)
>
> ie
> a sucessulf qurey would return rows 1,2 & n because they are all in
> the chain.
>
> Hope you can help me with my problem,

Re: Chain/Thread Problem

From
Richard Huxton
Date:
On Friday 16 May 2003 3:46 pm, Sammy wrote:
> Hi,
>
> I have a SQL problem for you all. What SQL qurey would I have to make
> on the following table to extract the chain (thread) of emails in a
> conversation.
>
>
>          id|emailid|referenceid
>          -----------------------
>           1|  e125 |   Null             (Start of chain)
>           2|  r1fe |   e125             (2nd letter in chain)
>           ...
>           ...
>           n|  e4ju |   r1fe             (3rd in chain)

Search the archives for "connect by", "hierarchy", "nested" and "celko" - this
is a limitation of SQL. In your particular case, I'd add a SERIAL "thread_id"
column which is autogenerated for the first msg in a thread and set to the
first message for all others.

You might want to check the contrib/ directory, I've got a feeling there's an
example table-function to do something like this.
--  Richard Huxton