[postgis-users] newbie query question

[Paul Ramsey]

That's actually a surprisingly tricky question (to solve efficiently).
The approach I have usually used is the counterintuitive one: do a
left join on the positive constraint (*is* within 100 meters) and the
return the rows that did *not* match the join (and therefore have null
unique id values in the resultant).

SELECT tbl_nla.gid FROM
tbl_nla LEFT JOIN tbl_rvb
ON ST_DWithin(tbl_nla.the_geom, tbl_rvb.the_geom, 100)
WHERE tbl_rvb.gid IS NULL;

P.

On Wed, Jun 9, 2010 at 2:06 PM, G. van Es <gves2000 at yahoo.com> wrote:
> I have two tables. tbl_nla has points as geometry and tbl_rvb has multipolygons.
>
> We want to list all the points of tbl_nla with no objects of tbl_rvb within 100 metres.
>
> Can anyone point me in the right direction?
>
> Thanks,
> Ge
>
>
>
>
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