Categories:: Semi-structured and structured data functions (Parsing)

CHECK_XML¶

Checks the validity of an XML document. If the input string is NULL or a valid XML document, the output is NULL. In case of an XML parsing error, the output string contains the error message.

See also:: PARSE_XML, TO_XML, XMLGET

Syntax¶

CHECK_XML( <string_containing_xml> [ , <disable_auto_convert> ] )

CHECK_XML( STR => <string_containing_xml>
  [ , DISABLE_AUTO_CONVERT => <disable_auto_convert> ] )

Arguments¶

Required:

string_containing_xml OR STR => string_containing_xml: Specify an expression that evaluates to a VARCHAR value that contains valid XML.

Optional:

disable_auto_convert OR DISABLE_AUTO_CONVERT => disable_auto_convert

Specify the same value that you pass to the PARSE_XML function.

Default: FALSE

Returns¶

The data type of the returned value is VARCHAR.

Usage notes¶

When you mix arguments by position and by name, all of the positional arguments must come before all of the named arguments.
When you specify an argument by name, you can’t use double quotes around the argument name.

Examples¶

The following examples use the CHECK_XML function.

Show the output of the function when the XML is valid¶

SELECT CHECK_XML('<name> Valid </name>');

+-----------------------------------+
| CHECK_XML('<NAME> VALID </NAME>') |
%-----------------------------------%
| NULL                              |
+-----------------------------------+

Show the output of the function when the XML is invalid¶

SELECT CHECK_XML('<name> Invalid </WRONG_CLOSING_TAG>');

+--------------------------------------------------+
| CHECK_XML('<NAME> INVALID </WRONG_CLOSING_TAG>') |
%--------------------------------------------------%
| no opening tag for </WRONG_CLOSING_TAG>, pos 35  |
+--------------------------------------------------+

Locate records with invalid XML¶

SELECT xml_str, CHECK_XML(xml_str)
  FROM my_table
  WHERE CHECK_XML(xml_str) IS NOT NULL;