Re: Unique constraint and NULL values

See the answer below.

"Mark C. Stock" <mcstockX_at_Xenquery .com> wrote in message news:zsqdnU_QrsleJurcRVn-vA_at_comcast.com...
> "Agoston Bejo" <gusz1_at_freemail.hu> wrote in message
> news:cl8ba7$d04$1_at_news.caesar.elte.hu...
> | I want to enforce such a constraint on a column that would ensure that
the
> | values be all unique, but this wouldn't apply to NULL values. (I.e.
there
> | may be more than one NULL value in the column.)
> | How can I achieve this?
> | I suppose I would get the most-hated "table/view is changing,
> | trigger/function may not see it" error if I tried to write a trigger
that
> | checks the uniqueness of non-null values upon insert/update.
> |
> |
>
> did you try a standard UNIQUE constraint on the column?

Yes, I did, and (1, null) and (1, null) couldn't be inserted twice. The Oracle version I'm currently using (or to be more exact forced to use) is 8.1.7. Maybe in later versions this was corrected, I don't know. Here, when I tried it, it worked the way I described in my original post.

>
> unlike SQL-Server (unless they've changed it since I last worked on it),
> Oracle processes null values properly in this scenario (i.e., one NULL
value
> is never consider equal to another NULL value)
>
> ++ mcs
>
>
Received on Thu Oct 21 2004 - 17:03:58 CEST