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<TITLE>RE: [postgis-users] Intersection - No GID</TITLE>
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<P><FONT SIZE=2>Marcus,<BR>
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.<BR>
<BR>
2) select area2d(Intersection(f.the_geom, c.the_geom)) ...<BR>
NOTE: You will have to convert this area2d result from the units of your map projection into acres<BR>
<BR>
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.<BR>
<BR>
HTH,<BR>
Robert<BR>
<BR>
-----Original Message-----<BR>
From: postgis-users-bounces@postgis.refractions.net on behalf of Marcus C. England<BR>
Sent: Tue 6/3/2008 2:57 PM<BR>
To: PostGIS Users Discussion<BR>
Cc: <BR>
Subject: [postgis-users] Intersection - No GID<BR>
<BR>
Hi all,<BR>
<BR>
I figured out how to use Intersection and get a resulting table with<BR>
apparently correct results using the example from the PostGIS website:<BR>
<BR>
CREATE TABLE new_fields AS<BR>
SELECT<BR>
Intersection(f.the_geom, c.the_geom) AS the_geom,<BR>
f.attr1,<BR>
f.attr2,<BR>
c.clu_name<BR>
FROM<BR>
fields f,<BR>
clu c<BR>
WHERE<BR>
f.the_geom && c.the_geom<BR>
AND<BR>
Intersects(f.the_geom, c.the_geom)<BR>
<BR>
However, this example does not create a gid column and I therefore can<BR>
not view the results in a GIS program. Is there a way to create a gid<BR>
column after-the-fact?<BR>
<BR>
Optional questions for those feeling super-helpful:<BR>
<BR>
(1) How should the above SQL be rewritten to include gid in the<BR>
resulting table?<BR>
<BR>
(2) I know that eliminating the first line will simply give me a table<BR>
spit onto the SQL results in pgAdmin. How do I alter the SQL above to<BR>
give me the acreages rather then a list of the geometries? I can get the<BR>
acreages from the table resulting from the above, but I can't figure out<BR>
how to skip the step of creating a table.<BR>
<BR>
(3) What is the syntax using ST_Intersection rather than Intersection?<BR>
<BR>
thanks,<BR>
<BR>
Marcus<BR>
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