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Date: Tue, 09 Nov 2004 19:29:49 -0800
To: pgsql-sql@postgresql.org
From: "Dean Gibson (DB Administrator)" <postgresql4@ultimeth.com>
Subject: Is NULLIF nullable?
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Recently I asked about why a field from the nullable side of an OUTER JOIN 
was causing the JOIN to be inefficient, and was told that it was because 
that field had a CASE statement as part of its definition, and that CASE 
(and by extension COALESCE) were non-nullable constructs.

Is NULLIF nullable, in that sense?

Reason:  I'd like to define a VIEW with a field definition thusly:

'P.O. Box' || NULLIF( po_box, ' '::char ) AS ...

And I would like the field thusly defined to be nullable.

-- Dean