[GRASS-user] v.db.* commands in GRASS-7

[Markus Metz]

Andres Kuusk wrote:
>
>
> Hi!
>
> It seems to me that some v.db.* modules do not do what is described in the
> manual.
>
> I am using GRASS-7.0 r51370 and Postgres data base.
>
> In the manual I read: It is possible to link the geographic objects in a
> vector map to one or more tables.
> All vector objects are kept in one geometry file, and topology is
> maintained for all vector objects together. GRASS layers only consist of
> links to different attribute tables in which vector objects can have zero,
> one or more categories.
>
> I link two attribute tables to a vector of area polygons.
> In layer 1 I see area polygons and I can use selection with where
> conditions on the attribute table 1.
>
> In layer 2 the same polylines are boundaries and selection in the
> attribute table 2 does not work. Maybe I am doing something wrong?

Before you can link an attribute table to a new layer, categories must
be set for that layer, not in the attribute table but in the vector
features, e.g. with v.category op=add layer=2.

You can check if any categories exist for layer 2 with v.category op=report

HTH,

Markus M


>
>
> Another problem.
> Command v.db.join returns error.
> I am trying to join two attribute tables (era2011 linked to the vector of
> area polygons era2011 with key=cat, and erb2011) of the same size:
>
> % v.db.join map=era2011 layer=1 column=cat otable=erb2011 ocolumn=erid
>
> Column cat in table era2011 is of type integer.
> Column erid in table erb2011 is of type smallint.
>
> I got an error:
>
> Adding column <erid> to the table
> DBMI-PostgreSQL driver error:
> Unable to execute:
> ALTER TABLE era2011 ADD COLUMN erid INTEGER(2)
> ERROR:  syntax error at or near "("
> LINE 1: ALTER TABLE era2011 ADD COLUMN erid INTEGER(2)
> ERROR: Error while executing: 'ALTER TABLE era2011 ADD COLUMN erid
> INTEGER(2)'
> ERROR: Unable to add column <erid INTEGER(2)>.
> ERROR: Error creating column <erid>
>
>
> The same error (syntax error at or near "(") I got in case the
> integer columns in the otable are of type integer (integer(4)).
>
>
> The v.db.join works if the first table (era2011) already has empty columns
> which correspond to the columns of the otable (erb2011).
>
> Does this mean that I have first to add columns to the attribute table of
> layer 1 and after that the v.db.join can be used for updateing attribute
> values in these columns?
>
>
> Thanks for advices!
>
>
> Andres Kuusk
> Tartu Observatory, Estonia
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