Re: Functional Dependency to constrain a relation to exactly one element?
From: Bob Badour <bbadour_at_pei.sympatico.ca>
Date: Mon, 02 Oct 2006 12:04:18 GMT
Message-ID: <6f7Ug.1636$%6.37430_at_ursa-nb00s0.nbnet.nb.ca>
>
> Typo!
>
> var R relation { ... } key { };
Date: Mon, 02 Oct 2006 12:04:18 GMT
Message-ID: <6f7Ug.1636$%6.37430_at_ursa-nb00s0.nbnet.nb.ca>
Alfredo Novoa wrote:
> Alfredo Novoa wrote:
>
>>var R { ... } key { };
>
> Typo!
>
> var R relation { ... } key { };
Alfredo,
I think he was referring to the existential constraint. Assuming the dbms treats DEE as true, all one needs to provide for the constraint is a projection onto zero attributes:
var R relation { ... } key {} constraint {}, insert R ...; Received on Mon Oct 02 2006 - 14:04:18 CEST