Markus and Gábriel:
Thank you very much for the help.
Yes, the table is redundant. What I am trying to do is using pgdijstra
module from postGIS which is on the top of postgreSQL. And the module
asks for entire network is directional or non-directional. But my
network part is directional and other part is non-directional. I made it
is directional by duplicate all non-directional edges into 2 directional
edges and it is where redundant come from. And the module only accept
data from one table, so I have to keep all data in one table.
Thanks again.
Fay
-----Original Message-----
From: pgsql-sql-owner@postgresql.org
[mailto:pgsql-sql-owner@postgresql.org] On Behalf Of Gábriel Ákos
Sent: Tuesday, March 28, 2006 12:34 PM
To: pgsql-sql@postgresql.org
Subject: Re: [SQL] Update question
Markus Schaber wrote:
> Hi, Fay,
>
> Fay Du wrote:
>> Table cost
>>
>> Id edge_id cost
>> 1 30 101.4
>> 2 30 null
>> 3 40 500.2
>> 4 40 null
>> 5 45 300.7
>> 6 45 null
>
>> I want to set cost value with same edge_id by same value. The
existing
>> values are calculated by calling a function (calculate edge length).
I
>> can calculate the value by same function, but the function was slow.
I
>> wander if I can use update statement to set the second value with
same
>> edge_id. Thanks in advance for your help.
>
> It should go like:
>
> UPDATE cost SET edge_id = (SELECT cost FROM cost innr WHERE
innr.edge_id
> = edge_id AND innr.cost is not null) WHERE cost is null;
>
> HTH,
> Marku
>
This is ok, but this is redundant, i guess. you should put edge_id and
cost into another table and use join to retrieve cost for each id.
put a key on edge_id, most likely a primary (unique) key.
--
Üdvözlettel,
Gábriel Ákos
-=E-Mail :akos.gabriel@i-logic.hu|Web: http://www.i-logic.hu=-
-=Tel/fax:+3612367353 |Mobil:+36209278894 =-
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