2011-10-17 14:28 keltezéssel, Susanne Ebrecht írta:
On 17.10.2011 10:30, Simon Riggs wrote:
On Mon, Oct 17, 2011 at 8:31 AM, Susanne Ebrecht
<susa...@2ndquadrant.com> wrote:
PostgreSQL isn't supporting CHAR(0).
What does the SQL Standard say?
Document: 02-Foundation
Section: 4.2.1 Introduction to character strings
Begin quoting
A character string is a sequence of characters. All the characters in a character string
are taken from a single
character set. A character string has a length, which is the number of characters in the
sequence. The length is
0 (zero) or a positive integer.
End quoting
I am looking at 6WD2_02_Foundation_2007-12.pdf.
Search for "<character length>" that is used in section "6.1 <data type>":
<character length> := <unsigned integer> [ <char length units> ]
Section 6.1 doesn't talk about limiting the definition to > 0 values
But in page 157, section "5.3 <literal>":
============================================================
17) The declared type of a <character string literal> is fixed-length character string.
The length of a <character
string literal> is the number of <character representation>s that it contains. Each <quote
symbol> contained
in <character string literal> represents a single <quote> in both the value and the length
of the <character
string literal>. The two <quote>s contained in a <quote symbol> shall not be separated by
any <separator>.
NOTE 92 — <character string literal>s are allowed to be zero-length strings (i.e., to
contain no characters) even though it is
not permitted to declare a <data type> that is CHARACTER with <character
length> 0 (zero).
============================================================
So, a table column is not allowed to be char(0) or varchar(0). It's explicit in
NOTE 92.
Best regards,
Zoltán Böszörményi
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Zoltán Böszörményi
Cybertec Schönig& Schönig GmbH
Gröhrmühlgasse 26
A-2700 Wiener Neustadt, Austria
Web: http://www.postgresql-support.de
http://www.postgresql.at/
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