[postgis-users] Intersection - No GID

[Marcus C. England]

Thank you... this did the trick.

Obe, Regina wrote:
> Marcus,
>  
> Just to add to some things that Robert said.
>  
> 1) You can also add the serial after the fact with a
> ALTER TABLE new_fields ADD COLUMN gid serial;
> ALTER TABLE new_fields  ADD CONSTRAINT pk_new_fields PRIMARY KEY(gid);
>  
> 3) ST_Intersects is different from Intersects although ST_Intersection 
> is the same as Intersection.  It includes the && operator so you can 
> leave out the && in it
>  
> CREATE TABLE new_fields AS
>  SELECT
>    ST_Intersection(f.the_geom, c.the_geom) AS the_geom,
>    f.attr1,
>    f.attr2,
>    c.clu_name
>  FROM
>    fields f,
>    clu c
>  WHERE
>     ST_Intersects(f.the_geom, c.the_geom)
>  
> Hope that hleps,
> Regina
>
> ------------------------------------------------------------------------
> *From:* postgis-users-bounces at postgis.refractions.net 
> [mailto:postgis-users-bounces at postgis.refractions.net] *On Behalf Of 
> *Burgholzer,Robert
> *Sent:* Tuesday, June 03, 2008 3:07 PM
> *To:* marcuscengland at gmail.com; PostGIS Users Discussion; PostGIS 
> Users Discussion
> *Subject:* RE: [postgis-users] Intersection - No GID
>
> Marcus,
> 1) You could create your table prior to populating it, and include a 
> column that is type "SERIAL", this will create an autogenerated 
> integer identifier that you could name "gid" if you so desired.
>
> 2) select area2d(Intersection(f.the_geom, c.the_geom)) ...
> NOTE: You will have to convert this area2d result from the units of 
> your map projection into acres
>
> 3) ST_intersection and intersection are the same, the new (ST_*) 
> naming convention was recently added, for reasons that I do not know 
> but assume that they were good ones.
>
> HTH,
> Robert
>
> -----Original Message-----
> From:   postgis-users-bounces at postgis.refractions.net on behalf of 
> Marcus C. England
> Sent:   Tue 6/3/2008 2:57 PM
> To:     PostGIS Users Discussion
> Cc:    
> Subject:        [postgis-users] Intersection - No GID
>
> Hi all,
>
> I figured out how to use Intersection and get a resulting table with
> apparently correct results using the example from the PostGIS website:
>
> CREATE TABLE new_fields AS
>  SELECT
>    Intersection(f.the_geom, c.the_geom) AS the_geom,
>    f.attr1,
>    f.attr2,
>    c.clu_name
>  FROM
>    fields f,
>    clu c
>  WHERE
>    f.the_geom && c.the_geom
>  AND
>    Intersects(f.the_geom, c.the_geom)
>
> However, this example does not create a gid column and I therefore can
> not view the results in a GIS program. Is there a way to create a gid
> column after-the-fact?
>
> Optional questions for those feeling super-helpful:
>
> (1) How should the above SQL be rewritten to include gid in the
> resulting table?
>
> (2) I know that eliminating the first line will simply give me a table
> spit onto the SQL results in pgAdmin. How do I alter the SQL above to
> give me the acreages rather then a list of the geometries? I can get the
> acreages from the table resulting from the above, but I can't figure out
> how to skip the step of creating a table.
>
> (3) What is the syntax using ST_Intersection rather than Intersection?
>
> thanks,
>
> Marcus
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