Is there such a thing as field replicants in MediaBin?

System

I am an IA working on a design. I may not be using the correct terminology for what I am trying to discover, which could be why I cannot find it in the manuals.

I need to replicate a metadata field. What is this called in common SQL? And is this available in MediaBin?

Detail: I have a photo containing more then one product. Each product has its own product number. I want to use a pull down list of Prod_Num to populate the field "Product_Number." Is there a "best practice" for this? Am I using the correct terminology? I am happy to have multiple Prod_Num fields associated with any image.

Thanks
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