[postgis-users] Two geometries same column

[Bob Pawley]

Thanks Johannes

That worked very well.

Bob
----- Original Message ----- 
From: "Johannes Sommer" <johann.online at gmx.de>
To: "PostGIS Users Discussion" <postgis-users at postgis.refractions.net>; 
<rjpawley at shaw.ca>
Sent: Saturday, July 25, 2009 12:14 PM
Subject: Re: [postgis-users] Two geometries same column


> Hi Bob,
>
> you can put alias names to the same column and use them in your statement:
>
> select a.geometry, b.geometry from sometable a, sometable b
>
> so in your case it would be something like:
>
> update p_id.image
>  set one =
> (select st_makeline(st_centroid(a.the_geom), st_centroid(b.the_geom))
>  from p_id.image a, p_id.image b
>  where (a.fluid_id =  '1513'
>  and a.description = 'A')
>  and (b.fluid_id = '1513'
>  and b.description = 'B'))
>
> bye,
> Johannes
>
>
> Bob Pawley schrieb:
>> Hi
>>
>> I ahve two geometries say A and B in the same column.
>>
>> I want to make a line between geometry A and geometry B.
>>
>> How can I write the expression so that Postgresql recognizes that A
>> and B are in separate rows?
>>
>> I have tried the following which produces a null return.
>>
>> update a --p_id.image
>>   set one = --the_geom =
>> (select
>> st_makeline(st_makepoint(st_x(st_centroid(p_id.image.the_geom)),
>> st_y(st_centroid(p_id.image.the_geom))),
>>   st_centroid(p_id.image.the_geom))
>>   from p_id.image
>>   where (p_id.image.fluid_id =  '1513'
>>   and p_id.image.description = 'A')
>>   and (p_id.image.fluid_id = '1513'
>>   and p_id.image.description = 'B'))
>>
>> Bob
>> ------------------------------------------------------------------------
>>
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>