Re: foreign key constraint versus referential integrity constraint

From: paul c <>
Date: Mon, 26 Oct 2009 15:16:38 GMT
Message-ID: <q3jFm.50312$PH1.43131_at_edtnps82>

Mr. Scott wrote:
> I'm not really sure what you mean by "The 'OR' disappears." An insert into
> a union view is inherently ambiguous.
> ...

I wasn't thinking of views. The person who wishes to assert all the propositions in a base relation AND some other proposition uses some language verb that is defined on UNION. Eg., if A is base, INSERT I INTO A 'loses' the 'OR'. He has used a disjunction to form a conjunction.

(By the way, I thought the regulars here knew better than to get me going on view updates! But since the door has opened if briefly, I'll comment that I've never understood why insert to base is treated as an instruction that produces a conjunction but the definition of a union view is not treated as such an instruction. I gather this is generally considered either heretical or cranky, possibly because it might play hob with de Morgan etc.) Received on Mon Oct 26 2009 - 16:16:38 CET

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