You want to export the result of a query as an XML document.

mysql can do that, or you can write your own exporter.

You can use mysql to produce XML-format output from a query result (Producing HTML or XML Output).

You can also write your own XML-export program. One way to do this is to issue the query and then write it out, adding all the XML markup yourself. But it’s easier to install a few Perl modules and let them do the work:

The following script, mysql_to_xml.pl, is somewhat similar to mysql_to_text.pl (Writing Your Own Export Programs), but doesn’t take options for such things as the quote or delimiter characters. They are unneeded for reading XML, because that is done by standard XML parsing routines. The options that mysql_to_xml.pl does understand are:

If necessary, you can also specify standard connection parameter options such as --user or --host. The final argument on the command line should be the database name, unless it’s implicit in the query.

Suppose that you want to export the contents of an experimental-data table expt that looks like this:

mysql>SELECT * FROM expt;
+---------+------+-------+
| subject | test | score |
+---------+------+-------+
| Jane    | A    |    47 |
| Jane    | B    |    50 |
| Jane    | C    |  NULL |
| Jane    | D    |  NULL |
| Marvin  | A    |    52 |
| Marvin  | B    |    45 |
| Marvin  | C    |    53 |
| Marvin  | D    |  NULL |
+---------+------+-------+

To do that, invoke mysql_to_xml.pl using either of the following commands:

%mysql_to_xml.pl --execute="SELECT * FROM expt" cookbook > expt.xml
% mysql_to_xml.pl --table=cookbook.expt > expt.xml

The resulting XML document, expt.xml, looks like this:

<?xml version="1.0" encoding="UTF-8"?>
<rowset>
 <select query="SELECT * FROM expt">
  <row>
   <subject>Jane</subject>
   <test>A</test>
   <score>47</score>
  </row>
  <row>
   <subject>Jane</subject>
   <test>B</test>
   <score>50</score>
  </row>
  <row>
   <subject>Jane</subject>
   <test>C</test>
  </row>
  <row>
   <subject>Jane</subject>
   <test>D</test>
  </row>
  <row>
   <subject>Marvin</subject>
   <test>A</test>
   <score>52</score>
  </row>
  <row>
   <subject>Marvin</subject>
   <test>B</test>
   <score>45</score>
  </row>
  <row>
   <subject>Marvin</subject>
   <test>C</test>
   <score>53</score>
  </row>
  <row>
   <subject>Marvin</subject>
   <test>D</test>
  </row>
 </select>
</rowset>

Each table row is written as a <row> element. Within a row, column names and values are used as element names and values, one element per column. Note that NULL values are omitted from the output.

The script produces this output with very little code after it processes the command-line arguments and connects to the MySQL server. The XML-related parts of mysql_to_xml.pl are the use statements that pull in the necessary modules and the code to set up and use the XML objects. Given a database handle $dbh and a query string $query, there’s not a lot to this process. The code instructs the writer object to send its results to the standard output, and then connects that object to DBI and issues the query:

#!/usr/bin/perl
# mysql_to_xml.pl - given a database and table name,
# dump the table to the standard output in XML format.

use strict;
use warnings;
use DBI;
use XML::Generator::DBI;
use XML::Handler::YAWriter;

#... process command-line options (not shown) ...

# ... connect to database (not shown) ...

# create output writer; "-" means "standard output"
my $out = XML::Handler::YAWriter->new (AsFile => "-");
# set up connection between DBI and output writer
my $gen = XML::Generator::DBI->new (
              dbh => $dbh,            # database handle
              Handler => $out,        # output writer
              RootElement => "rowset" # document root element
            );
# issue query and write XML
$gen->execute ($stmt);

$dbh->disconnect ();

Other languages might have library modules to perform similar XML export operations. For example, the Ruby DBI::Utils::XMLFormatter module has a table method that easily exports a query result as XML. Here’s a simple script that uses it:

#!/usr/bin/ruby -w
# xmlformatter.rb - demonstrate DBI::Utils::XMLFormatter.table method

require "Cookbook"

stmt = "SELECT * FROM expt"
# override statement with command line argument if one was given
stmt = ARGV[0] if ARGV.length > 0

begin
  dbh = Cookbook.connect
rescue DBI::DatabaseError => e
  puts "Could not connect to server"
  puts "Error code: #{e.err}"
  puts "Error message: #{e.errstr}"
end

DBI::Utils::XMLFormatter.table(dbh.select_all(stmt))

dbh.disconnect