Regarding your Issue 1, I'd do the same that is recommended for any type of programming: factor out the things that are common, and store the rest separately.

For your MANAGER and NON_MANAGER example that would be a table EMPLOYEE or PERSON that stores all common data (like address, payment etc) and a MANAGER-table for all data that only appears for managers.

Perl 6 in German

In reply to Re: (OT) Couple of Data Model Design Considerations by moritz
in thread (OT) Couple of Data Model Design Considerations by Anonymous Monk

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