[GRASS-user] Change the length and type of columns in an attribute table

[Camille Bezzina]

Ok thanks Markus for your answer.

But I have another question :

I have 2  differents vectors with the same attribute table structure.

This problem is just for one of them.

For the first vector the attribute table is like that :

 > name     type                              length
 >
 > cat                      integer 20
 > ID                       character                       24
 > PREC_PLANI       double precision             20
 > NATURE              character                       31
 > HAUTEUR           integer                            20
 > id_2                    integer  20

and for the second :

 > name                   type                    length
 >
 > cat                      integer   20
 > ID                       text                       1000
 > PREC_PLANI       double precision             20
 > NATURE             text                      1000
 > HAUTEUR           integer                            20
 > id_2                    integer  20

So when I want to patch my 2 vectors with v.patch, there is the 
following message :

(Thu Apr  5 15:01:50 2018)
v.patch -e --overwrite --verbose 
input=zone_vegetation_D90_decoupe at AIP_RONCHAMP_MNE,zone_vegetation_D70_decoupe at AIP_RONCHAMP_MNE 
output=TEST_merge_D70_D90
ERROR: Length of string columns differ
(Thu Apr  5 15:01:51 2018) La commande s'est terminée (1 sec)




Le 05/04/2018 à 14:41, Markus Metz a écrit :
>
>
> On Wed, Apr 4, 2018 at 5:54 PM, Camille Bezzina 
> <camille.bezzina at geophom.fr <mailto:camille.bezzina at geophom.fr>> wrote:
> >
> > Hello all,
> >
> >
> > I have a problem when I want to modify an attribute table.
> >
> > I add a new vector with v.in.ogr. My attribute table is build like 
> that :
> >
> > name                   type  length
> >
> > cat                      integer   20
> > ID                       character 24
> > PREC_PLANI       double precision             20
> > NATURE              character                       31
> > HAUTEUR           integer                            20
> > id_2                    integer  20
> >
> >
> > I would like to remove the column 'HAUTEUR', but when I remove this
> > column, my two character columns (ID and NATURE) change automatically to
> > become :
> >
> > ID                   text        1000
> > NATURE         text        1000
> >
> > Do you know why the simple fact to remove a column (HAUTEUR) change type
> > and length of other columns.
>
> The reason is that GRASS uses SQLite as database manager, and in 
> SQLite there is nothing like varchar(24), only text without any length 
> restrictions. That means, when importing vector data with attributes, 
> any text fields are converted to text by SQLite itself. The value 1000 
> as length for text is somewhat misleading here because the maximum 
> allowed length in SQLite is by default 1 billion.
>
> Markus M
> >
> > Thanks,
> > --
> >
> > Camille BEZZINA
> > Chargé d'études géomatiques et photomontages
> > Geophom
> > 57 rue du Chemin Neuf 44521 OUDON
> > Standard: +33(0)2 85 52 02 59
> > Ligne directe: +33(0)9 72 56 81 71
> > www.geophom.fr <http://www.geophom.fr>
> >
> > _______________________________________________
> > grass-user mailing list
> > grass-user at lists.osgeo.org <mailto:grass-user at lists.osgeo.org>
> > https://lists.osgeo.org/mailman/listinfo/grass-user
>

-- 
Camille BEZZINA
Chargé d'études géomatiques et photomontages
Geophom
57 rue du Chemin Neuf 44521 OUDON
Standard: +33(0)2 85 52 02 59
Ligne directe: +33(0)9 72 56 81 71
www.geophom.fr
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