Re: Surrogate primary key plus unique constraint vs. natural primary key: data integrity?

From: <robur.6_at_gmail.com>
Date: Tue, 19 Mar 2013 03:00:04 -0700 (PDT)
Message-ID: <cd56444f-6e1d-49cd-9d04-aa374798e30b_at_googlegroups.com>

On Monday, March 18, 2013 8:22:02 PM UTC+2, Jan Hidders wrote:
> Why would we need views for that

Because surrogates do not carry information, so you can�t write constraints based on their values. In practice you may need to replace simple check constraints with some SELECT / WHERE constructs (which is not well supported).

>/ And if we do replace composites by surrogates?

Because if (a,b) <=> (x) and (b,c) <=>(y) then {(a,b) and (b,c)} is not equivalent to (x,y) (you replace a join by a product). So you will need some other constraint. Received on Tue Mar 19 2013 - 11:00:04 CET

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