Re: URGENT: Primary key vs Unique Index

Bill Bearden wrote:
>
> There are two important differences between Primary and Unique Keys.
>
> 1. There can only be one Primary Key on a table. There can be more than
> one column with Unique Key.
> 2. Primary Key columns can't contain NULL. Unique Key columns can.
>

Pardon my ignorance but why can't a primary key be NULL ? Is it a rule or is it specific to just Oracle ?

rgds,
mars Received on Tue Feb 25 1997 - 00:00:00 CST