John Hunter wrote:
>
> Is there a normalization rule that indicates that there must be an unique PK
> key on every table in the database? I am having a debate with a co-worker
> and one of us says that there has to be one and the other disagrees. Who is
> right?
>
> Thanks,
> -John
My take is that both of you have some element of 'The Truth'
(with you being closer than your co-worker).
- Unique PK key is redundant (a PK identifies rows uniquely).
- A table can have more than one unique key (that is also
somewhat redundant).
- I will argue that it should be possible to define a
PK for any useful table (the key may be a composite
across all columns of the table).
- But not all tables need (or should) have this key declared as part
of their table definition. There are real-world examples
where the table structure has been so denormalized and
twisted that the necessary composite index would be almost
as large as the table itself, and rarely used.
Instead, smaller indexes which identify small chunks of
the table will be used.
--
Phil Singer | psinger1_at_chartermi.net
Oracle DBA
Go Wings!!!!!!!
Received on Thu May 02 2002 - 18:08:10 CDT
