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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
-
-
-->
<refentry id="fn_XMLFOREST">
<refmeta>
<refentrytitle>XMLFOREST</refentrytitle>
<refmiscinfo>xml</refmiscinfo>
</refmeta>
<refnamediv>
<refname>XMLFOREST</refname>
<refpurpose>Produces a forest of XML elements</refpurpose>
</refnamediv>
<refsynopsisdiv>
<funcsynopsis id="fsyn_XMLFOREST">
<funcprototype id="fproto_XMLFOREST">
<funcdef>
<function>XMLFOREST</function>
</funcdef>
<paramdef>
<parameter>string_expr1 [AS alias1]</parameter> varchar</paramdef>
<paramdef>
<optional>
<parameter>string_expr2 [AS alias2]</parameter> varchar</optional>
</paramdef>
<paramdef>
<optional>
<parameter>...</parameter>
</optional>
</paramdef>
<paramdef>
<optional>
<parameter>string_exprN [AS aliasN]</parameter> varchar</optional>
</paramdef>
</funcprototype>
</funcsynopsis>
</refsynopsisdiv>
<refsect1 id="desc_XMLFOREST">
<title>Description</title>
<para>
<function>XMLFOREST</function> produces a forest of XML elements from the given list of arguments.
The arguments may be string expressions with optional aliases. If string expression is a column name,
then you can omit the AS clause, and Virtuoso uses the partially escaped form of
the column name as the name of the enclosing tag. If the expression evaluates to NULL, then no element is
created for that expression. If none of the element is created, then the function returns NULL.
</para>
</refsect1>
<refsect1 id="XMLFOREST">
<title>Parameters</title>
<refsect2>
<title>string_exprI [AS aliasI]</title>
<para>string value; AS clause is mandatory if the argument is not a column name but an expression of some other sort.</para>
</refsect2>
</refsect1>
<refsect1 id="errors_XMLFOREST">
<title>Errors</title>
<table>
<title>Errors signalled by <function>XMLFOREST</function>
</title>
<tgroup cols="4">
<thead>
<row>
<entry>SQLState</entry>
<entry>Error Code</entry>
<entry>Error Text</entry>
<entry>Description</entry>
</row>
</thead>
<tbody>
<row>
<entry>
<errorcode>37000</errorcode>
</entry>
<entry>
<errorcode>SQ074</errorcode>
</entry>
<entry>
<errorname>The special SQL function has invalid argument</errorname>
</entry>
<entry>An argument is neither a column name nor an expression with an alias.</entry>
</row>
</tbody>
</tgroup>
</table>
<para/>
</refsect1>
<refsect1 id="XMLFOREST">
<title>Examples</title>
<example id="ex_XMLFOREST">
<title>XMLFOREST() with five parameters.</title>
<para>
The following example produces five (or four) elements ('FName', 'LName', 'str', 'Title', and 'Region' - if there is a value)
from the string expressions 'FirstName', 'LastName', 'string', 'Title', and 'Region',
concatenates the elements produced for each
employee, and produces one row for each employee in the result set.
</para>
<screen>
select XMLFOREST (
"FirstName" as "FName", "LastName" as "LName",
'string' as "str", "Title", "Region" )
from "Demo"."demo"."Employees";
callret
VARCHAR
_______________________________________________________________________________
<FName>Nancy</FName>
<LName>Davolio</LName>
<str>string</str>
<Title>Sales Representative</Title>
<Region>WA</Region>
. . .
<FName>Anne</FName>
<LName>Dodsworth</LName>
<str>string</str>
<Title>Sales Representative</Title>
9 Rows.
</screen>
<para>
The following example always produces five elements: empty 'Region' element is created for NULL values.
Note the difference in the last rows of this and the previous query results:
</para>
<screen>
select XMLFOREST (
"FirstName" as "FName", "LastName" as "LName",
'string' as "str", "Title", coalesce ("Region", '') as "Region")
from "Demo"."demo"."Employees";
callret
VARCHAR
_______________________________________________________________________________
<FName>Nancy</FName>
<LName>Davolio</LName>
<str>string</str>
<Title>Sales Representative</Title>
<Region>WA</Region>
. . .
<FName>Anne</FName>
<LName>Dodsworth</LName>
<str>string</str>
<Title>Sales Representative</Title>
<Region></Region>
9 Rows.
</screen>
</example>
</refsect1>
<refsect1 id="seealso_XMLFOREST">
<title>See Also</title>
<para>
<link linkend="fn_XMLELEMENT">XMLELEMENT()</link>
</para>
<para>
<link linkend="fn_XMLATTRIBUTES">XMLATTRIBUTES()</link>
</para>
<para>
<link linkend="fn_XMLAGG">XMLAGG()</link>
</para>
<para>
<link linkend="fn_XMLCONCAT">XMLCONCAT()</link>
</para>
</refsect1>
</refentry>
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