FairFunk (7/16/2010)
Currently I have a supertype > Subtype relationship set up with Organisation being the super type and charity, company and trust being the subtypes. The organisation Super type contains the attribute PRIMARY ADDRESS which all three subtypes’ inherit.However only charity and company require the attribute Registered address (not the subtype Trust).
As I see it Subtypes are created to track differences in between different flavors of the Supertype e.g. different attributes are needed in different subtypes of the same supertype.
Following that line of thinking I would include "primary address" in the supertype - it will be inherited by the three subtypes - then track the differences in the subtypes, in this case I'll include the attribute "registered address" in the Charity and Company subtypes.
Hope this helps.
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Pablo (Paul) Berzukov
Author of Understanding Database Administration available at Amazon and other bookstores.
Disclaimer: Advice is provided to the best of my knowledge but no implicit or explicit warranties are provided. Since the advisor explicitly encourages testing any and all suggestions on a test non-production environment advisor should not held liable or responsible for any actions taken based on the given advice.