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Commit 41a40fe4 authored by Bruce Momjian's avatar Bruce Momjian
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CVS NULL Documentation

Clearify documentation of CVS's output of NULL values, per suggestion
from Magnus.

Backpatch to 8.4.X.
parent 44608aee
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<!--
$PostgreSQL: pgsql/doc/src/sgml/ref/copy.sgml,v 1.87 2009/09/05 23:58:01 tgl Exp $
$PostgreSQL: pgsql/doc/src/sgml/ref/copy.sgml,v 1.88 2009/09/17 21:13:01 momjian Exp $
PostgreSQL documentation
-->
......@@ -550,13 +550,10 @@ COPY <replaceable class="parameter">count</replaceable>
<para>
The <literal>CSV</> format has no standard way to distinguish a
<literal>NULL</> value from an empty string.
<productname>PostgreSQL</>'s <command>COPY</> handles this by
quoting. A <literal>NULL</> is output as the <literal>NULL</>
string and is not quoted, while a data value matching the
<literal>NULL</> string is quoted. Therefore, using the default
settings, a <literal>NULL</> is written as an unquoted empty
string, while an empty string is written with double quotes
(<literal>""</>). Reading values follows similar rules. You can
<productname>PostgreSQL</>'s <command>COPY</> handles this using
quoting. A <literal>NULL</> is output as an empty string without
quotes, while an empty string data value is double-quoted
(<literal>""</>). Reading values follows similar rules. You can
use <literal>FORCE NOT NULL</> to prevent <literal>NULL</> input
comparisons for specific columns.
</para>
......
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