I have a silly question that I can't wrap my head around doing more
efficiently (and it may not actually matter).
My example is that I have two tables, tax parcels from the county, and
the USGS streams center lines.
Say I want to select all parcels within a meter of a stream center line
(yeah, it's a silly query, as at least one of those "streams" is 25
meters wide). I can do:
SELECT par_parcels.the_geom FROM par_parcels , hyd_usgsstrm
WHERE ST_DWithin(par_parcels.the_geom, hyd_usgsstrm.the_geom, 1)
But that, of course, gives me multiple par_parcels.
I can also do:
SELECT DISTINCT(par_parcels.the_geom) FROM par_parcels , hyd_usgsstrm
WHERE ST_DWithin(par_parcels.the_geom, hyd_usgsstrm.the_geom, 1)
But what I really want is something more like:
SELECT the_geom FROM par_parcels
WHERE ST_DWithin(the_geom, (SELECT the_geom FROM hyd_usgsstrm), 1);
but that, of course, both doesn't let the query optimizer do anything
intelligent and gives me:
ERROR: more than one row returned by a subquery used as an expression
What's the right approach for this kind of query?
Thanks!
Dan
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