Thanks, Robert. I thought I read that the newer functions beginning with
"ST_" allow you to simplify the expressions, but I am not sure how. When
you are new to this, I think simpler is better (at least easier to learn!).
-Marcus
Burgholzer,Robert wrote:
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: [EMAIL PROTECTED] 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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