Adrian Kubala wrote:
> shannon <shannon_at_nolunchmeat.com> schrieb:
>>I have tried an example from the elmasri book, perhaps somebody can pass
>>judgement on my logic,
>>
>>two sets of functional dependencies F= {A > C, AC > D, E > AD, E > H}
>>and G = {A > CD, E > AH}. Check whether or not they are equivalent.
>>
>>here I make conclusion that they are not equivalent
>
> I don't know about the official way to do this, but by inspection C > D
> is derivable from F but not G, so they can't be equivalent.
How do you derive C -> D from F? It can't be from AC -> D, but I
don't see where else you can think it comes from either.
--
Jonathan Leffler #include <disclaimer.h>
Email: jleffler_at_earthlink.net, jleffler_at_us.ibm.com
Guardian of DBD::Informix v2003.04 -- http://dbi.perl.org/
Received on Thu Jan 08 2004 - 22:32:45 CST
