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<?xml version="1.0" encoding="ISO-8859-1"?>
<!--
-
- This file is part of the OpenLink Software Virtuoso Open-Source (VOS)
- project.
-
- Copyright (C) 1998-2018 OpenLink Software
-
- This project is free software; you can redistribute it and/or modify it
- under the terms of the GNU General Public License as published by the
- Free Software Foundation; only version 2 of the License, dated June 1991.
-
- This program is distributed in the hope that it will be useful, but
- WITHOUT ANY WARRANTY; without even the implied warranty of
- MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
- General Public License for more details.
-
- You should have received a copy of the GNU General Public License along
- with this program; if not, write to the Free Software Foundation, Inc.,
- 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
-
-
-->
<!--
Please use the following prefixes for IDs:
xpf_ for old XPATH functions,
xf_ for XPATH 2.0 & XQUERY 1.0 functions,
xsl_ for XSL elements,
-->
<refentry id="xpf__sql__column">
<refmeta>
<refentrytitle>sql:column</refentrytitle>
<refmiscinfo>XQuery</refmiscinfo>
</refmeta>
<refnamediv>
<refname>sql:column</refname>
<refpurpose>Returns the value of a column from SQL result-set.</refpurpose>
</refnamediv>
<refsynopsisdiv>
<funcsynopsis id="xpf_syn__sql__column">
<funcprototype id="xpf_proto__sql__column">
<funcdef>any <function>sql:column</function></funcdef>
<paramdef>constant <parameter>column_name</parameter> varchar</paramdef>
</funcprototype>
</funcsynopsis>
</refsynopsisdiv>
<refsect1 id="xpf_desc__sql__column"><title>Description</title>
<para>This is actually not a function but a special macro that is
converted to a reference to a global parameter.
</para>
</refsect1>
<refsect1 id="xpf_params__sql__column"><title>Parameters</title>
<refsect2><title>column_name</title>
<para>A string constant (literal, not an expression)
that is a column name in plain SQL syntax. It can be a column name
(and it can be qualified to specify a table name or an alias name).
It can be a name of a Virtuoso/PL variable.
</para>
<para>The string should not contain quotes around parts of the column name.
</para>
</refsect2>
</refsect1>
<refsect1 id="xpf_ret__sql__column"><title>Return Types</title>
<para>The value of the sql:column() invocation is the value of some
SQL column or variable. If the type of the value is not supported by XQuery
interpreter then it will be converted according to generic rules for
XQuery parameters.</para>
</refsect1>
<refsect1 id="xpf_examples__sql__column"><title>Examples</title>
<example id="xpf_ex__sql__column"><title>Various invocations of sql:column</title>
<para>These two statements will produce identical results:</para>
<screen></screen>
</example>
</refsect1>
<refsect1 id="xpf_seealso__sql__column"><title>See Also</title>
<para><link linkend="xq_precompilation">Pre-compilation of XPath and XQuery Expressions</link></para>
</refsect1>
</refentry>
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