[GRASS-user] updating table values from another table
mlennert at club.worldonline.be
Tue May 13 18:22:23 EDT 2008
On 13/05/08 16:38, Manuel Seeger wrote:
> Hello all,
> I want to update the values of selected columns in one vector file with
> the values from another. I think v.db.update should be the right thing,
> but I don't know ho to do it (using the dbf driver)
> Perhaps someone helps me?
This really depends on which backend you are using. If you use dbf data
files, the only way to do it would be v.db.join to join the complete
tables together as dbf tables are not "conscious" of each other.
If you use another backend (e.g. PostgreSQL or SQLite), the easiest
would probably to do this directly in the database, without going
through GRASS. The SQL would be something like this:
UPDATE A SET name = B.name FROM B WHERE A.id = B.id
However, you can also use db.execute:
echo "UPDATE A SET name = B.name FROM B WHERE A.id = B.id" | db.execute
or put into the SQL into file and call db.execute with the file= parameter.
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