I would thought that like 'select * from table' which extract all fields with having to specify all the fields individually, SQLQuery.Update or Insert would have similar feature instead of having to specify each Field-Value pair.
You don't have to specify each field value pair with .edit.
You can just change the field you want to change.
If you are worried about speed, this is still very fast and the easiest way.
Otherwise you can follow Trons suggestion to create a separate sql.update but that's more work. It's up to you. Otherwise I'm not sure your explaining your problem correctly.