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From: Dean Gibson (DB Administrator) <postgresql4@ultimeth.com>
To: pgsql-sql@postgresql.org
Subject: Is NULLIF nullable?
Date: Tue, 09 Nov 2004 19:29:49 -0800
Message-ID: <5.1.0.14.2.20041109192441.00ae3f68@imaps.mailpen.net> (raw)
In-Reply-To: <25393.1095739813@sss.pgh.pa.us>
References: <5.1.0.14.2.20040920182022.00adf5e8@imaps.mailpen.net>
	<5.1.0.14.2.20040920164348.00a99868@imaps.mailpen.net>
	<5.1.0.14.2.20040920121606.00a89c68@imaps.mailpen.net>
	<414F02FF.8000603@numerixtechnology.de>
	<414F02FF.8000603@numerixtechnology.de>
	<5.1.0.14.2.20040920121606.00a89c68@imaps.mailpen.net>
	<5.1.0.14.2.20040920164348.00a99868@imaps.mailpen.net>
	<5.1.0.14.2.20040920182022.00adf5e8@imaps.mailpen.net>

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




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