Well basically, each time you submit a catalog item, the variables of that catalog item will be stored in table sc_item_option. So the problem is when you do transform map from a attachment contains the variable's values, you can't not make a coalesce field on those variables because those are not fixed variables, they're created everytime you submit a catalog item, therefore they will always get inserted, not updated to the target field of variables that you want them to be updated.
