From: Don Drake <dondrake@gmail.com>
To: pgsql-sql@postgresql.org
Subject: Re: NULLS and string concatenation
Date: Fri, 19 Nov 2004 14:21:39 -0600
Message-ID: <6c21003b0411191221325695ad@mail.gmail.com> (raw)
In-Reply-To: <13631.1100894502@sss.pgh.pa.us>
References: <6c21003b0411190912630d4afe@mail.gmail.com>
<419E31F2.4060104@archonet.com>
<6c21003b041119104039c88faf@mail.gmail.com>
<13631.1100894502@sss.pgh.pa.us>
On Fri, 19 Nov 2004 15:01:42 -0500, Tom Lane <tgl@sss.pgh.pa.us> wrote:
> Don Drake <dondrake@gmail.com> writes:
> > This is still strange to me. In Oracle, the same query would not
> > replace the *entire* string with a NULL, it treats the NULL as a no
> > value.
>
> Oracle is a bit, um, standards-challenged. They fail to make a
> distinction between an empty string and a NULL, but such a distinction
> is both logically necessary and required by the SQL standard.
>
> > I can't find in the documentation where string concatenation of any
> > string and NULL is NULL.
>
> SQL92 section 6.13 <string value expression>, General Rule 2a:
>
> a) If either S1 or S2 is the null value, then the result of the
> <concatenation> is the null value.
>
> regards, tom lane
>
Thanks for the responses. I now have a better appreciation for the
SQL standard and PostgreSQL.
-Don
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To: pgsql-sql@postgresql.org
Cc: dondrake@gmail.com
Subject: Re: NULLS and string concatenation
In-Reply-To: <6c21003b0411191221325695ad@mail.gmail.com>
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