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Name

XMLType.extract — Evaluates given XPATH expression.

Synopsis

XMLType.extract ( in xpath_expn varchar ,
  in namespace_map varchar );
 

Description

The member function calculates the given XPATH expression xpath_expn using the XML entity of the instance as a context node. If a namespace_map parameter is given then the function adds namespace declarations from this parameter into the beginning of xpath_expn before the evaluation. The function returns the first result of the XPATH evaluation or NULL if there are no results. If the result is an XML entity then it is converted into a non-schema based instance of XMLType.

Parameters

xpath_expn

A text of XPATH expression to evaluate.

namespace_map

A string that is a list of namespace prefix declarations delimited by whitespace characters. If the xpath_expn expression also contains a list of declarations then these two lists are concatenated.

Return Types

The function returns a non-schema based XMLType instance, NULL or a value of any other type

Examples

Example 24.548. A table with an XMLType column

This populates a table with XML data and then selects 'ename' element from the appropriate record. 

create table TEST_XMLS  (I integer primary key, XMLVAL XMLType);
insert into TEST_XMLS  values (1, XMLType('<emp><empno>221</empno><ename>John</ename></emp>'));
insert into TEST_XMLS  values (2, XMLType('<po><pono>331</pono><poname>PO_1</poname></po>'));
insert into TEST_XMLS  values (3, XMLType('<oil-rig
xml:id="14a_01" water="0.413"/><oil-rig
xml:id="14b_01" water="0.402"/>'));
select e.XMLVAL.extract ('//ename').getCLobVal() as ENAME
  from TEST_XMLS  as e
  where e.XMLVAL.existsNode('/emp/empno')
ENAME
NVARCHAR
_______________________________________________________________________________

<ename>John</ename>

1 Rows. -- 00000 msec.

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