Hi Kevin, this is what I needed, thank You very much. Interesting idea to use aliases this way, I learned something new, thank You for the lesson also ;)
Tomas On Mon, 2010-01-04 at 14:35 -0800, Kevin Neufeld wrote: > I think you can do this with a simple UPDATE statement. > > postgis=# select id, asewkt(geom), distance from pts; > id | asewkt | distance > ----+---------------+---------- > 1 | POINT(0 1 7) | > 2 | POINT(0 3 7) | > 3 | POINT(0 6 7) | > 4 | POINT(0 12 7) | > 5 | POINT(0 55 7) | > (5 rows) > > > UPDATE pts a > SET distance = st_length3d(st_makeline(a.geom, b.geom)) > FROM pts b > WHERE a.id + 1 = b.id; > > > postgis=# select id, asewkt(geom), distance from pts order by id; > id | asewkt | distance > ----+---------------+---------- > 1 | POINT(0 1 7) | 2 > 2 | POINT(0 3 7) | 3 > 3 | POINT(0 6 7) | 6 > 4 | POINT(0 12 7) | 43 > 5 | POINT(0 55 7) | > (5 rows) > > -- Kevin > > Tomas Lanczos wrote: > > Dear all, > > > > I am not sure whether am I using correct terminology in the subject, so > > I will try to explain my problem: > > > > I am trying to write a spatial query to measure a a 3D distance between > > two neighboring points. The basic query I prepared is the following: > > > > "UPDATE particle_set_3dps set distance = (SELECT > > ST_length3d(ST_MakeLine((SELECT particle_set_3dps.the_geom from > > particle_set_3dps where id = 1), (SELECT particle_set_3dps.the_geom > > from particle_set_3dps WHERE id = 2)))) where id = 1; " > > > > What I need further is the distance between points with id = 2 and id = > > 3, between id=3 and id=4, between id=4 and id=5 etc. ... > > > > I assume that it is not so complicated to write a query for that, but I > > never needed it until now and I don't know what therms to use as > > keywords to find an answer somewhere, also due to my poor English (shame > > on me, I know ... ;)). > > > > Best regards and many thanks in advance > > > > Tomas > > > > _______________________________________________ > > postgis-users mailing list > > [email protected] > > http://postgis.refractions.net/mailman/listinfo/postgis-users > _______________________________________________ postgis-users mailing list [email protected] http://postgis.refractions.net/mailman/listinfo/postgis-users
