Re: FW: Informix versus Oracle Spatial

"Superboer" <superboer7_at_planet.nl> wrote in message news:1133532431.734359.218240_at_z14g2000cwz.googlegroups.com...
> Just tryed:
>
> create table nullix( a int, b char(10), primary key(a));
>
> insert into nullix (b) values ('One ');
>
> ---- error does not allow null in col a ...
>
> So obstacle is dictating to have a PK which does not allow nulls in my
> table...
>
> this:
> create table nullix( a int unique , b char(10));
>
> insert into nullix (b) values ('One ');
> insert into nullix (b) values ('One Dupl');
> insert into nullix (b) values ('Two Dupl');
>
> succeeds....
>
>> Absolutely. null is absence of any information about a datum,
>> how can you know that it is a duplicate? It might well not be.
>
> sorry mate i disagree with you on that
>
> select * from nullix where a is null
>
> gives me the info.
>
> so sqlnul is sqlnul and also sqlnull in an index and is a unique value;
>
> to get the real answer i guess one has to goto the sql specs.
> -- haven't got them; any takers....???
>
>
> Superboer.
>

....

not quite following all the comments, but i think this post is about whether NULL values are considered duplicate (equal) or unique

AFAIK, according to the SQL Standard two NULL values by definition are never considered equal -- however SQL Server muddies things up (considerably) by not allowing multiple NULL values in a UNIQUE index. Oracle and others correctly allow multiple NULL values in a UNIQUE index

++ mcs Received on Fri Dec 02 2005 - 08:51:24 CST