We're trying to implement a SQL update in a vortex script. Is there any way to check the return value to see if the update was successful or how many rows were changed?
Yes. The Vortex script will loop over and return the updated values of the rows as if you had done a select, so you can check $loop at the end of the SQL, or you can put a check inside the SQL loop.
When you don't care about the values of the fields that are in the record you can specify NOVARS which will stop Vortex from storing them in memory. $loop will still be set correctly though.