[GRASS-user] Join sqlite table by coordinate pair (X,Y)

GRASS GRASS user
1

On 23/10/12 6:00 AM, grass-user-request@lists.osgeo.org wrote:

Message: 1
Date: Mon, 22 Oct 2012 13:20:02 +0200
From: Johannes Radinger<johannesradinger@gmail.com>
To:grass-user@lists.osgeo.org
Subject: [GRASS-user] Join sqlite table by coordinate pair (X,Y)
Message-ID:
  <CABsGe_xs1NHvOhGX_vvW=fe_afVf-ptkzB2kESa1xUOcw5GJOg@mail.gmail.com>
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Hi,

I have a points vector file with the columns X and Y which are
populated with the respective coordinates.
Additionally I have a .csv file for the same points, also with the X
and Y column and a lot more columns
providing additional information. These two files don't share a single
unique key which can be used for joining.

Thus I'd like to use the X-Y pair as a key for importing and then
joining the csv table
to the vector. Is there any possibility to use two columns as a
combined key instead of one
(probably an SQL statement for db.execute)? Or do I need to first
create a new column
and combine x and y into a key for the vector and the csv?

Any suggestions how that can be done in GRASS (6.5, sqlite) in a simple way?

Best regards,
Johannes

My suggestion -

Map_a = your sqlite map
Map_b = the csv file

1. Import the csv file as Map_b
2. Add a column to Map_b to capture the categories in Map_A (a_cat)
3. Use v.distance to populate the "a_cat" column in Map_b
4. v.db.connect Map_a table=Map_b key=a_cat layer=2

Step 4 means that the second table is now connected to your original map, using the same category values as the key.

cheers,
Richard