I'm going to clarify something; I said most data has a natural key then when presented with this and other examples I seemed to have backed away from that. I ho

I'm going to clarify something; I said most data has a natural key then when presented with this and other examples I seemed to have backed away from that. I hope this makes sense... In the real world of atoms etc. there's no natural abstraction, including unique IDs (keys). These are all creations of ours. In my line(s) of work, someone's invented and allocated a key for most items by the time it's reached me - people have SSN/NI numbers, planes will have some identifier, ships have IMOs, machine parts have unique part numbers (when combined with their suppliers' ID), geographical areas have postcodes/zipcodes, and all that. So for me, someone's done that work already; a 'natural key' is available and I can rely on it. It's always been there, except for a few things such as addresses. For you, willvarfar, customer numbers have to be created. So I made a wide assertion without thinking it through based just on my experience.