Interesting, but that assumes there's a value to use in the coalesce that isn't a valid data value.
__________________________________________________________________________________
Mike Blackwell | Technical Analyst, Distribution Services/Rollout Management | RR Donnelley
1750 Wallace Ave | St Charles, IL 60174-3401
Office: 630.313.7818
Mike.Blackwell@rrd.com
http://www.rrdonnelley.com
On Tue, Sep 25, 2012 at 10:32 AM, hubert depesz lubaczewski
<depesz@depesz.com> wrote:
On Tue, Sep 25, 2012 at 10:05:15AM -0500, Mike Blackwell wrote:
> How would one go about building a multi-column unique constraint where null
> is a significant value, eg. (1, NULL) <> (2, NULL)?
>
> I see a number of references to not being able to use an index for this,
> but no mention of an alternative. Any pointers would be appreciated
create unique index zzz on table ((column is null), coalesce(column, 'whatever'));
Best regards,
depesz
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