MySQL:

UPDATEXML

Syntax:
UpdateXML(xml_target, xpath_expr, new_xml)

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.

URL: https://dev.mysql.com/doc/refman/8.0/en/xml-functions.html

Example

mysql> SELECT
-> UpdateXML('<a>ccc<d></d></a>', '/a', '<e>fff</e>') AS val1,
-> UpdateXML('<a>ccc<d></d></a>', '/b', '<e>fff</e>') AS val2,
-> UpdateXML('<a>ccc<d></d></a>', '//b', '<e>fff</e>') AS val3,
-> UpdateXML('<a>ccc<d></d></a>', '/a/d', '<e>fff</e>') AS val4,
-> UpdateXML('<a><d></d>ccc<d></d></a>', '/a/d', '<e>fff</e>') AS val5
-> \G

*************************** 1. row ***************************
val1: <e>fff</e>
val2: <a>ccc<d></d></a>
val3: <a><e>fff</e><d></d></a>
val4: <a>ccc<e>fff</e></a>
val5: <a><d></d>ccc<d></d></a>