Can I create a LOV where the index is created on the fly, not taken from a table?

Application Express 4.2.5.00.08

I need to create a List Of Values (LOV) of the coulmn Unit Part Number (UPN) for project ‘EVAL SYSTEMS’ in APEX, from table PIMS_COMPONENTS. I am aware a LOV in APEX needs to be in the form {Value, ID} for each row., but as there is no ID column as such in the table I tried creating a row number of my own and this query appears to give me the 5 rows I want:

select distinct unit_part_number d, DENSE_RANK() OVER (ORDER BY unit_part_number) as r from pims_component where project_id = 'EVAL SYSTEMS'