[GRASSLIST:7315] db.execute trouble

[Aldo Clerici]

Dear GRASS community,
can somebody tell me why the UPDATE operation works with a simple
assignement like in:
echo "UPDATE soils SET area=1000 WHERE area > 200"| db.execute
but return an error with any kind of operation like for example:
echo "UPDATE soils SET area=area+1 WHERE area > 200"| db.execute
or even simply:
echo "UPDATE soils SET area=1+1 WHERE area > 200"| db.execute

The output error is:
DBMI-DBF driver error:
SQL parser error in statement:
UPDATE suoli SET area=area+1 WHERE area > 200"
Error in db_execute_immediate ()
ERROR: Error while executing: "UPDATE suoli SET area=area+1 WHERE area > 200
"

Many thanks to everybody

Aldo Clerici
Parma University