Re: Help: What is the difference between UNIQUE and PRIMARY KEY?

Steve Bell wrote:
>
> A unique field requires that each entry be different (unique) from every
> other record OR NULL.
>
> A primary key imposes a second condition, namely the NOT NULL
> condition...so, the field must be both unique and not null.

   In addition table can have ONLY ONE PRIMARY KEY    and any number of UNIQUE KEYS (alternate key).

Valery Yourinsky
>
> u518615722_at_spawnkill.ip-mobilphone.net wrote:
>
> > I searched against metalink and could not find the
> > definition of unique index, could somebody help
> > me out?
> >
> > Thanks
> >
> >
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Oracle8 Certified DBA
Moscow, Russia