I think you want to create a look up table where each COD is in it's own record and there are no duplicates.
Define a table with the fields you need for your look up table.
For the COD field, specify a Unique Values, validate always validation rule.
Then Import all your records from your current table of All COD's into this new table mapping fields from one table to the other to get the data where you need it.
When this validation rule is enabled, the duplicates will be filtered out during the import process.
Thanks! Worked like a charm.