Re: 2NF There are two Definitions which is right

In article <3k7t18Ft6e3bU1@xxxxxxxxxxxxxx>, jens@xxxxxxxx says...
> I found two definitions for 2NF:
>
> 1: A relation R(A,F) is in 2NF, when every attribute not belonging to
> the primary key of R is fully functionally dependent on the primary key of R
>
> 2: A relation schema R is in 2NF if every nonprime attribute A in R is
> fully functionally dependent on the primary key of R
[8<]
> Which definition is right?

The second. Normalisation theory doesn't deal with the arbitrary primary
key distinction. The first definition probably makes the assumption that
there is only one key.
--
Jon
.

Relevant Pages

  • Re: 2NF There are two Definitions which is right
    ... A relation Ris in 2NF, when every attribute not belonging to the primary key of R is fully functionally dependent on the primary key of R ... A relation schema R is in 2NF if every nonprime attribute A in R is fully functionally dependent on the primary key of R ... key distinction. ... Given that prime attributes are components of some candidate key, the second is marginally more correct, but would be more convincingly so if it finished 'dependent on each candidate key of R'. ...
    (comp.databases.theory)
  • Re: 2NF There are two Definitions which is right
    ... >> the primary key of R is fully functionally dependent on the primary key ... Normalisation theory doesn't deal with the arbitrary primary ... authors make a single primary key assumption when introducing normalization ...
    (comp.databases.theory)
  • 2NF There are two Definitions which is right
    ... A relation Ris in 2NF, when every attribute not belonging to the primary key of R is fully functionally dependent on the primary key of R ... A relation schema R is in 2NF if every nonprime attribute A in R is fully functionally dependent on the primary key of R ... According to the first definition when the primary key is AB, then A->D violates 2NF, because D is not part of the primary key. ...
    (comp.databases.theory)