[postgis-users] I'm missing something

[Bob Pawley]

Re: [postgis-users] I'm missing somethingHi Regina

It gives me three rows each with the expression "ST_MultiLineString" with nothing else.

Bob
  ----- Original Message ----- 
  From: Obe, Regina 
  To: PostGIS Users Discussion 
  Sent: Tuesday, May 20, 2008 10:56 AM
  Subject: RE: [postgis-users] I'm missing something


  Bob,

  Strange. I don't think I have ever seen quite that error before.  What does

  SELECT ST_GeometryType(the_geom)
  FROM tank_lin;

  give you?

  Regina


------------------------------------------------------------------------------
  From: postgis-users-bounces at postgis.refractions.net on behalf of Bob Pawley
  Sent: Tue 5/20/2008 1:07 PM
  To: PostGIS Users Discussion
  Subject: Re: [postgis-users] I'm missing something


  I tried this -

  Insert into graphics.process_dgm(the_geom)
   Select   ST_Union(the_geom)
   from tank_lin;

  and got the error "Unknown geometry type: 0"

  Bob
  ----- Original Message -----
  From: "Paul Ramsey" <pramsey at cleverelephant.ca>
  To: "PostGIS Users Discussion" <postgis-users at postgis.refractions.net>
  Sent: Tuesday, May 20, 2008 9:51 AM
  Subject: Re: [postgis-users] I'm missing something


  > You don't want the GROUP BY. It is grouping the union op on distinct
  > geometry... ie, one per row. Remove it and you'll get what you want,
  > one output row.
  >
  > P
  >
  > On Tue, May 20, 2008 at 8:49 AM, Bob Pawley <rjpawley at shaw.ca> wrote:
  >> Hi
  >>
  >> I am attemptijng to use the ST_Union function to collapse three rows from
  >> a
  >> table called tank_lin into one row in table called process_dgm.
  >>
  >> Here's what I used -
  >> Insert into graphics.process_dgm(the_geom)
  >> Select   ST_Union(the_geom)
  >> from tank_lin
  >> Group by tank_lin.the_geom;
  >>
  >> The result is three rows inserted into process_dgm, each row appearing to
  >> be
  >> simple copies of each of the original rows.
  >> I also attempted group by another column but received error 'unknown
  >> geometry'.
  >>
  >> I also tried STR_LineMerge with similar results.
  >>
  >> What am I not considering?
  >>
  >> Bob
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