That worked; sublimely simple. Thank you!
On Mon, Sep 27, 2010 at 3:43 PM, Richard Greenwood <[email protected]> wrote: > I think this should do the trick: > > SELECT EXTENT(the_geom) > FROM parcels_public > WHERE gid > 27611 AND gid < 28000; > > > Rich > > > > > On Mon, Sep 27, 2010 at 9:05 AM, John Poole <[email protected]> wrote: >> I've been grappling with the following concept and reviewing the >> PostGIS 1.5.1 Manual and cannot seem to come up with a working >> solution to achieve this simple goal: >> >> GOAL: I want to collect various polygons and then determine the >> bounding box or extent of the collection in order to display an >> appropriately zoomed image on MapServer >> >> Here's the SQL I'm starting with: >> >> select the_geom from parcels_public where gid > 27611 and gid < 28000 >> returns >> 388 rows of geometries. >> >> How do I create a geometry collection from a set of rows? I've been >> looking at ST_Collect and trying: >> >> * * * warning below is bad code * * * >> Select ST_Collect((select the_geom from parcels_public where gid > >> 27611 and gid < 28000)) as myCollectionObject >> >> which produces: >> ERROR: more than one row returned by a subquery used as an expression >> >> ********** Error ********** >> >> ERROR: more than one row returned by a subquery used as an expression >> SQL state: 21000 >> >> * * * >> >> Referencing the thread in the documentation, >> http://postgis.refractions.net/pipermail/postgis-users/2008-June/020331.html >> , >> I tried this >> >> * * * warning below is bad code * * * >> SELECT ST_Multi(ST_Collect(f.the_geom)) as singlegeom >> FROM ( >> SELECT ( >> select the_geom >> from parcels_public >> where gid > 27611 and gid < 27640 >> ) >> ) As f >> which produces: >> ERROR: column f.the_geom does not exist >> LINE 1: SELECT ST_Multi(ST_Collect(f.the_geom)) as singlegeom >> ^ >> >> ********** Error ********** >> >> ERROR: column f.the_geom does not exist >> SQL state: 42703 >> Character: 28 >> * * * >> >> I know this can be done, but I seemed to be missing something very >> basic both in creating subqueries and in the documentation and I'm >> confusing structure, e.g. rows returned vs. a geometry collection. >> Maybe my problem is that I do not know how to construct a geometry >> collection from a given set of rows? >> >> The end goal is to have the coordinates of the collection so I can use >> them as an extent to send to MapServer to create an image that is >> zoomed into the minimum size that displays all members of the >> collection. I anticipate using ST_Extent(myCollectionObject) once I'm >> able to create the collection object. >> >> -- >> John L. Poole >> >> P.O. Box 6566 >> Napa, CA 94581-6566 >> 707-812-1323 >> >> [email protected] >> _______________________________________________ >> postgis-users mailing list >> [email protected] >> http://postgis.refractions.net/mailman/listinfo/postgis-users >> > > > > -- > Richard Greenwood > [email protected] > www.greenwoodmap.com > _______________________________________________ > postgis-users mailing list > [email protected] > http://postgis.refractions.net/mailman/listinfo/postgis-users > -- John L. Poole P.O. Box 6566 Napa, CA 94581-6566 707-812-1323 [email protected] _______________________________________________ postgis-users mailing list [email protected] http://postgis.refractions.net/mailman/listinfo/postgis-users
