[postgis-users] sql/function which returns points within certain distance?

[Twan Kogels]

Thanks, i tryed the sql query and it worked perfect. It does exactly what i 
needed!

Best regards,
Twan Kogels

At 09:51 22-5-2002 -0700, you wrote:
>select * from pttable where the_geom &&
>GeometryFromText('BOX3D($pt_x - $radius  $pt_y - $radius,$pt_x + $radius
>$pt_y + $radius)'::box3d,-1)
>and distance(the_geom, GeometryFromText('POINT($pt_x $pt_y)',-1)) <
>$radius;
>
>What is happening here? We have an index-based 'overlap query' going on
>first, using the && operator, followed by a slower distance() test. We
>count on the optimizer to figure out to do the && test first and then
>the distance() test. If we did not trust the optimizer we could simple
>next the && query inside the distance() query with a sub-select.
>
>Twan Kogels wrote:
> >
> > Hello,
> >
> > I have put a point layer (.shp) with many points in a postgresql database,
> > i've done this with the shp2pgsql tool supplied with the postgis 
> distribution.
> >
> > When i let Mapserver load the layer with a postgis connection, all points
> > appear correct.
> >
> > I'm now reading the postgis/sql functions of postgis and i'm wondering if
> > it is possible to create a query which returns all points within a distance
> > of 10 km. from a center point.
> >
> > To illustrate my question i have made a picture:
> > http://www.gdeesha.com/bin/center.gif
> >
> > As you can see the picture contains several black points, the blue point is
> > the center point. The red circle is the 10 km circle. Is it possible that a
> > sql query will return only the black point in the red circle?
> >
> > (The circle may also be replaced by a rectangle)
> >
> > Best regards,
> > Twan Kogels
> >
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>
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