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CVS NULL Documentation

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

Backpatch to 8.4.X.
This commit is contained in:
Bruce Momjian 2009-09-17 21:28:30 +00:00
parent 010394d7aa
commit 77b2388b24
1 changed files with 6 additions and 9 deletions
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11
doc/src/sgml/ref/copy.sgml
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@ -1,5 +1,5 @@
<!-- <!--
$PostgreSQL: pgsql/doc/src/sgml/ref/copy.sgml,v 1.85 2009/02/06 21:22:49 tgl Exp $ $PostgreSQL: pgsql/doc/src/sgml/ref/copy.sgml,v 1.85.2.1 2009/09/17 21:28:30 momjian Exp $
PostgreSQL documentation PostgreSQL documentation
--> -->
@ -544,12 +544,9 @@ COPY <replaceable class="parameter">count</replaceable>
<para> <para>
The <literal>CSV</> format has no standard way to distinguish a The <literal>CSV</> format has no standard way to distinguish a
<literal>NULL</> value from an empty string. <literal>NULL</> value from an empty string.
<productname>PostgreSQL</>'s <command>COPY</> handles this by <productname>PostgreSQL</>'s <command>COPY</> handles this using
quoting. A <literal>NULL</> is output as the <literal>NULL</> quoting. A <literal>NULL</> is output as an empty string without
string and is not quoted, while a data value matching the quotes, while an empty string data value is double-quoted
<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 (<literal>""</>). Reading values follows similar rules. You can
use <literal>FORCE NOT NULL</> to prevent <literal>NULL</> input use <literal>FORCE NOT NULL</> to prevent <literal>NULL</> input
comparisons for specific columns. comparisons for specific columns.