XPath expressions for filtering output
You can use an XPath expression to filter the XML output returned by a common SQL API stored procedure.
To filter the output, specify a valid XPath query string in the xml_filter parameter of the procedure. The following restrictions apply to the XPath expression that you specify:
- The XPath expression must reference a single value.
- The XPath expression must always be absolute from the root node.
For example, the following path expressions are allowed: /,
nodename
,.
, and..
. The following expressions are not allowed://
and@
- The only predicates allowed are
[path='value']
and[n]
. - The only axis allowed is
following-sibling
. - The XPath expression must end with one of the following, and,
if necessary, be appended with the predicate [1]:
following-sibling::string
,following-sibling:: data
,following-sibling::date
,following-sibling::real
, orfollowing-sibling::integer
. - Unless the axis is found at the end of the XPath expression, it
must be followed by a
::dict
,::string
,::data
,::date
,::real
, or::integer
, and if necessary, be appended with the predicate [1]. - The only supported XPath operator is
=
. - The XPath expression cannot contain a function, namespace, processing instruction, or comment.
Tip: If the stored procedure operates in complete
mode, do not apply filtering, or a SQLCODE (+20458) is raised.
For better control over processing the XML document returned in the xml_output parameter, you can use the XMLPARSE function available with Db2® pureXML®.
Example
The following XPath expression selects the value for the Data Server Product Version key from an XML output document:
/plist/dict/key[.='Data Server Product Version']following-sibling::string[1]
The procedure returns the string 8.1.0.356
in the xml_output parameter. Therefore, the procedure
call returns a single value rather than an XML document.