Sachbat,
Create a subscription view in MDS (This inturn creates a database view). Use this view to lookup with business key and insert code into staging table. If there is no match on the lookup then insert the record with blank code into staging table.
For example: - Lets consider you are loading Product entity from a source. Firstly, create a subscription view for this Product entity (lets name it as SV_Product). In the DFT, after the oledb source transformation, place the lookup task. The lookup task
will have SV_Product. Join on the ProductName from source and if the product name matches, insert corresponding code into staging table. If the join does not work, then insert the no match output records into staging table with blank or NULL codes.
Let me know if you need more details. Thanks.