Syntax
------

UpdateXML(xml_target, xpath_expr, new_xml)

Description
-----------

This function replaces a single portion of a given fragment of XML markup
xml_target with a new XML fragment new_xml, and then returns the changed XML.
The portion of xml_target that is replaced matches an XPath expression
xpath_expr supplied by the user. If no expression matching xpath_expr is
found, or if multiple matches are found, the function returns the original
xml_target XML fragment. All three arguments should be strings.

Examples
--------

SELECT
  UpdateXML('<a><b>ccc</b><d></d></a>', '/a', '<e>fff</e>') AS val1,
  UpdateXML('<a><b>ccc</b><d></d></a>', '/b', '<e>fff</e>') AS val2,
  UpdateXML('<a><b>ccc</b><d></d></a>', '//b', '<e>fff</e>') AS val3,
  UpdateXML('<a><b>ccc</b><d></d></a>', '/a/d', '<e>fff</e>') AS val4,
  UpdateXML('<a><d></d><b>ccc</b><d></d></a>', '/a/d', '<e>fff</e>') AS val5
  \G
*************************** 1. row ***************************
val1: <e>fff</e>
val2: <a><b>ccc</b><d></d></a>
val3: <a><e>fff</e><d></d></a>
val4: <a><b>ccc</b><e>fff</e></a>
val5: <a><d></d><b>ccc</b><d></d></a>
1 row in set (0.00 sec)

URL: https://mariadb.com/kb/en/updatexml/