[GRASS-user] concatenating/combining two table fields for multi-field join

[Timmie]

> How can I perform the corresponding command on the command for the GRASS
> table?
In 
http://grass.osgeo.org/grass65/manuals/sql.html I found:
v.db.update vectormap column=column3 qcolumn="column1 || column2"

running the command on my data yields:

#dbmi: Protocol error
#dbmi: Invalid procedure 107
#ERROR: Fehler beim Ausführen von: 'UPDATE vectormap SET joinkey="a_value

What causes this error and what could I do to prevent it?