Hi,
I have extended the v.db.update script:
support added to copy values from another query column in the table.
This can even be with calculation on the fly.
g.copy vect=fields,myfields
v.db.addcol myfields col="polynum integer"
v.db.update myfields col=polynum qcol="cat*2"
v.db.select myfields
cheers
Markus