Re: Primary Key/Unique Key?

Hi, All!

You can test it:

 SQL> create table qq(n number primary key);

 Table created.

 SQL> insert into qq values(null);
 insert into qq values(null)

             *
 ERROR at line 1:
 ORA-01400: mandatory (NOT NULL) column is missing or NULL during  insert

 SQL> drop table qq
   2 ;

 Table dropped.

 SQL> create table qq(n number unique);

 Table created.

 SQL> insert into qq values(null);

 1 row created.

 SQL> insert into qq values(null);

 1 row created.

 SQL> select * from qq;

         N

 SQL> insert into qq values(1);

 1 row created.

 SQL> insert into qq values(1);
 insert into qq values(1)

             *
 ERROR at line 1:
 ORA-00001: unique constraint (ABC.SYS_C001691) violated

Ergo:
unique <> primary

Best regards,
Ivan

Jurry wrote:

> I don't think there's really a difference.
>
> A primary key in a relational database is always unique!
>
> Dave <none_at_nowhere.nothere.oops> schreef in artikel
> <82ip3r$cuv$1_at_lure.pipex.net>...
> > Whats the difference between making something
> > a primary key and making something a unique key.
> > From Oracles point of view that is.
> > Dave
> >
> >
> >
> >
Received on Tue Dec 07 1999 - 10:21:12 CST