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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
-
-
-->
<sect1 id="xmltableview">
<title>Getting a Rowset from XML Data (OPENXML)</title>
<para>Whereas you can use the FOR XML clause to retrieve data as an XML
document, you can use the Virtuoso-SQL OPENXML function to insert data
represented as an XML document. OPENXML is a rowset generator similar to a
table or a view, providing a rowset over in-memory XML documents. OPENXML
allows access to XML data as if it is a relational rowset by providing a
rowset view of the internal representation of an XML document. The records
in the rowset can then be stored in database tables. OPENXML can be used in
SELECT, and SELECT INTO statements where a source table or view can be
specified.</para>
<para>To write queries against an XML document using OPENXML, you must
first call <emphasis>sp_xml_preparedocument</emphasis>, which parses the
XML document and returns a handle to the parsed document that is ready
for consumption. The parsed document is a tree representation of various
nodes (elements, attributes, text, comment, and so on) in the XML document.
The document handle is passed to OPENXML, which then provides a rowset
view of the document based on the parameters passed to it.</para>
<para>The internal representation of an XML document must be removed from
memory by calling <emphasis>sp_xml_removedocument</emphasis>
system stored procedure to free the memory.</para>
<para>This illustration shows the process.</para>
<figure id="xmlsp" float="1">
<title>Illustration showing the OPENXML process</title>
<graphic fileref="xmlsp.gif"/>
</figure>
<para>The following example shows the use of OPENXML in an INSERT statement
and a SELECT statement. The sample XML document consists of <Customers>
and <Orders> elements. First, the
<emphasis>sp_xml_preparedocument</emphasis> stored procedure parses the XML
document. The parsed document is a tree representation of the nodes (elements,
attributes, text, comments, and so on) in the XML document. OPENXML then
refers to this parsed XML document and provides a rowset view of all or parts
of this XML document. An INSERT statement using OPENXML can insert data from
such a rowset into a database table. Several OPENXML calls can be used to
provide a rowset view of various parts of the XML document and process them,
for example, inserting them into different tables (this process is also
referred to as "Shredding XML into tables"). In the following example, an XML
document is shredded in a way that <Customers> elements are stored in
the <emphasis>Customers</emphasis> table and <Orders> elements are
stored in the <emphasis>Orders</emphasis> table using two INSERT statements.
</para>
<para>The example also shows a SELECT statement with OPENXML that retrieves
<emphasis>CustomerID</emphasis> and <emphasis>OrderDate</emphasis> from the
XML document.</para>
<programlisting>
DECLARE @hDoc int
EXEC sp_xml_preparedocument @hDoc OUTPUT,
N'<ROOT>
<Customers CustomerID="XYZAA" ContactName="Joe"
CompanyName="Company1">
<Orders CustomerID="XYZAA"
OrderDate="2000-08-25T00:00:00"/>
<Orders CustomerID="XYZAA"
OrderDate="2000-10-03T00:00:00"/>
</Customers>
<Customers CustomerID="XYZBB" ContactName="Steve"
CompanyName="Company2">No Orders yet!
</Customers>
</ROOT>'
-- Use OPENXML to provide rowset consisting of customer data.
INSERT Customers
SELECT *
FROM OPENXML(@hDoc, N'/ROOT/Customers')
WITH Customers
-- Use OPENXML to provide rowset consisting of order data.
INSERT Orders
SELECT *
FROM OPENXML(@hDoc, N'//Orders')
WITH Orders
-- Using OPENXML in a SELECT statement.
SELECT * FROM OPENXML(@hDoc, N'/ROOT/Customers/Orders')
with (CustomerID nchar(5) '../@CustomerID', OrderDate datetime)
-- Remove the internal representation of the XML document.
EXEC sp_xml_removedocument @hDoc
</programlisting>
<figure id="xmlparsedtree" float="1">
<title>The parsed XML tree of the preceding XML documentation created by sp_xml_preparedocument</title>
<graphic fileref="xmlparsedtree.gif"/>
</figure>
&openxml;
</sect1>
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