title: Query xml using extract over CLOB column in Oracle
body: <p>We are storing the xml in oracle database. The column type is CLOB.
  I could fetch data from the xml tag with below query. When i execute the query i am getting null.</p>
  
  <p><strong>XML in the column:</strong></p>
  
  <pre><code>&lt;input xmlns="http://google.com/testsystem" 
         xmlns:testsystem="http://test.com/testSystem"          
         xmlns:tns="http://google.com/testService/"&gt;
        &lt;ProcessData&gt;      
          &lt;reviewYear&gt;2014-2015&lt;/reviewYear&gt;
        &lt;/ProcessData&gt;
      &lt;/input&gt;
  </code></pre>
  
  <blockquote>
    <p>Table name : test_table<br>
    Column name : input_xml<br>
    Column type : CLOB</p>
  </blockquote>
  
  <p><strong>Query:</strong> </p>
  
  <pre><code>select extract(xmltype(input_xml),'//reviewYear/text()').getStringVal() as data 
  from test_table 
  where id = 1;
  </code></pre>
  
  <p><strong>Result:</strong></p>
  
  <pre><code>DATA                  
  ------------------------------------
  </code></pre>