To add to what Paul said. ST_Extent is an aggregate function so you can use
in your case like (note: your insert syntax looks flawed by the way)
INSERT INTO country_extents (country, geom)
SELECT
country,ST_Extent(point)
FROM waypoint
GROUP BY country
However ST_ConvexHull is not an aggregate function. Hmm and I've never used
it, but I suspect you will have to do the below if you want convexhull for
the country.
INSERT INTO country_convexhull(country, geom)
SELECT country, ST_ConvexHull(ST_Collect(point))
FROM waypoint
GROUP BY country
I am assuming your points are POINT geometries and not MULTIPOINT. If
MULTIPOINT, you may need to replace ST_Collect with ST_UNION.
Hope that helps,
Regina
-----Original Message-----
From: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED] On Behalf Of Paul
Ramsey
Sent: Saturday, April 05, 2008 6:00 PM
To: PostGIS Users Discussion
Subject: Re: [postgis-users] bounday or convex hull of a bunch of points
st_extent for a minimal bounding box
st_convexhull for a hull
On Sat, Apr 5, 2008 at 1:08 PM, Paul Tomblin <[EMAIL PROTECTED]> wrote:
> I have a table with a point column. Is there a way to find the
> boundary or convex hull of some of the entries in that table? For
> instance, if I want to find the extents of each country in the table, can
I say
> insert into country_extents (country, geom) values (select
> country,
> ST_XXX(point) from waypoint group by country));
>
> --
> Paul Tomblin <[EMAIL PROTECTED]> http://blog.xcski.com/ "I'm
> cruising down the Information Superhighway in high gear, surfing the
> waves of the Digital Ocean, exploring the uncharted regions of Cyberspace.
> Actually I'm sitting on my butt staring at a computer screen."
> _______________________________________________
> postgis-users mailing list
> postgis-users@postgis.refractions.net
> http://postgis.refractions.net/mailman/listinfo/postgis-users
>
_______________________________________________
postgis-users mailing list
postgis-users@postgis.refractions.net
http://postgis.refractions.net/mailman/listinfo/postgis-users
_______________________________________________
postgis-users mailing list
postgis-users@postgis.refractions.net
http://postgis.refractions.net/mailman/listinfo/postgis-users
