Generates a forest of XML elements. In an unparsed XML document, a forest refers to the multiple root nodes within the document.
NULL values are omitted from the result. If all the values are NULL, then NULL is returned. The XMLCONCAT function does not
check whether the argument has a prolog. If you require a well-formed XML document, you must ensure that your query is written
so that a single root element is generated.
Element content is always escaped unless the data type is XML. Data in BINARY, LONG BINARY, IMAGE, and VARBINARY columns is
automatically returned in base64-encoded format when you execute a query that contains a XMLCONCAT function.