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Date: Thu, 7 Nov 2002 08:41:26 -0800 (PST)
From: Stephan Szabo <sszabo@megazone23.bigpanda.com>
To: Ludwig Lim <lud_nowhere_man@yahoo.com>
Cc: PostgreSQL Mailing List <pgsql-sql@postgresql.org>
Subject: Re: Weird NULL behavior
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On Thu, 7 Nov 2002, Ludwig Lim wrote:

> Hi:
>
>   Has anyone encountered this before?
>   SELECT CAST ( (NULL*NULL) AS NUMERIC(2,0));
>
>
>   returns the following error message:
>   Cannot cast type '"char"' to '"numeric"'

It seems to me that it's trying to decide on a type
for the expression NULL * NULL.  It's a NULL, but a
NULL of what type?  I think the spec gets around
this by disallowing such structures AFAIK (NULL
can be used in like row value constructors, case
and cast).  I think the "sql" way of doing the
above would be
select cast(cast(NULL as NUMERIC(2,0))*cast(NULL as NUMERIC(2,0))
 as NUMERIC(2,0));