[GRASS5] extend update command in GRASS SQL

Hello,

How difficult would it be to extend the capacities of the UPDATE command in
the GRASS SQL ?

If I understand correctly, at the moment all one can do is to update a column
to a given fixed value. I haven't found a way to either update it with the
value of another column or (more importantly) with an expression such as set
col3=col1/col2. This would be quite useful.

Moritz