Re: Functional dependencies

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От Darren Duncan
Тема Re: Functional dependencies
Дата
Msg-id 4DF7A87D.1080206@darrenduncan.net
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Ответ на Functional dependencies  (Alpha Beta <dzjitaru@gmail.com>)
Ответы Re: Functional dependencies  (Alpha Beta <dzjitaru@gmail.com>)
Список pgsql-general
Alpha Beta wrote:
> Hi list,  (newbie with databases)
>
> I was looking out in net about how can we determine or find all
> functional dependencies in a  relational database, but didn't find.
>
> So can please anyone here tell me if functional dependecies for each
> table of a relational database can be found explicitly or
> we need algorithms for it or any other way?
>
> Best regards!

Look for pairs of columns/attributes X and Y (or X may be a set of
columns/attrs) where, for every row/tuple having the same value for X, the
row/tuple always has the same value for Y.  In this situation, for the data you
have at least, there would seem to be a relationship where X determines Y and Y
depends on X.  Use an algorithm that does this looking for pairs. -- Darren Duncan


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