I'm not using the model anywhere in my code for updates.
Only inserts and selects.

But if I needed to do updates, the only way I would know how would be to
make your original table with an id primary key column (unique number value). Then use QsqlQuery to update the record where id = <id of row you want updated> The only column values that will be updated are the ones specified in your update statement - the other column values will remain unchanged.

Good Luck!