index duplicate records from data source into 1 document

[Derek Poh]

Hi

If I have duplicaterecords in my source data (DB or delimited files). 
For simplicity sake they are of the following nature

Product Id    Business Type
-----------------------------------
12345         Exporter
12345     Agent
12366     Manufacturer
12377         Exporter
12377 Distributor

There are other fields with multiple values as well.

How do I index theduplicate records into 1 document. Eg. Product Id 
12345 will be 1 document,12366 as 1 document and 12377 as 1 document.

-Derek