My approach to this is to use GUID's - they are guaranteed unique across all systems in the world until 3040. I don't plan on being around in 1,000 years to service my software.

GUID expressed as text requires 38 bytes (char (38) NOT NULL).

If Interbase ever gets a GUID data type it can be expressed as a 16 byte binary field.

This guarantees that I can merge similar tables across several dissimilar databases without ever worrying about uniqueness.

This also allows me the capacity for asymmetric relations, which opens up a whole world of potential for data and code versioning.

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