I can't mail it to:
postgis-users@postgis.refractions.netso could administrator forword this mail to them? thanks!
From:
sunpeng <bluevaley@gmail.com> Date: 2010/9/12
Subject: how to write the sql if i want to find a geometry's d-distance neighbors?
To:
postgis-users@postgis.refractions.net Hi,
I've the following table,and has created the index on uid and location;
CREATE TABLE points
(
location geometry, //assume it's a 2-dimension point
uid integer
)
Now, I've a point P with uid= 12345, and want to find the neighbors which are within 20, how to write the sql?Is this right?
select st_astext(location)
from points a, points b
where b.rid = 12345 and ST_DWithin(a.the_geom, b.the_geom, 20)
or use st_buffer? which one is more efficient ?
Thanks!