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,
or following-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.