Brent Wood wrote:
--- Stephen Woodbridge <[EMAIL PROTECTED]> wrote:
I think that should be geomunion, not union, in the SQL.
Right, good catch. Thanks.
Brent Wood
Jeff Dege wrote:
I have a shapefile that contains a few duplicated features.
They have identical attribute data, different OGRFeature numbers, and
different geometries.
I've imported them into PostGIS, but having two different records for
the same feature is causing some problems.
The schema is simple:
CREATE TABLE "public"."counties" (gid serial PRIMARY KEY,
"state" varchar(2),
"name" varchar(18),
"wtr" int2,
"fips" int4);
SELECT
AddGeometryColumn('public','counties','the_geom','4267','MULTIPOLYGON',2
);
The duplicates are easy to find:
select state, name, count(*)
from counties
group by state, name
having count(*) > 1
;
What I would like to do is to merge these duplicate records into a
single record, containing a union of the separate records' geometries.
But I'm not sure of exactly how to approach it.
Jeff,
Create a temp table
insert into temp (select state, name, wtr, fips, union(the_geom) from
countries group by states, name having count(*) > 1 );
check that it did what you expected, then delete the records by state,
name and insert the temp table records into the original table.
or you can alter you table to add a column which is used to track the
unioned records when they are added so you can delete the non-unioned
records that you don't want. You can alter the table to drop the column
when you are done.
-Steve
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