Oracle 18c

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CREATE TABLE table_name ( xml BLOB );
DECLARE
  value        CLOB := EMPTY_CLOB()
|| '<root>
  <entry>
    <string>NAME1</string>
    <string>VALUE1</string>
    <other><entry><string>NAME2</string><string>NOT THIS</string></entry></other>
  </entry>
  <entry>
    <string>NAME2</string>
    <string>VALUE2</string>
  </entry>
</root>';

  dest_offset  INTEGER := 1;
  src_offset   INTEGER := 1;
  lang_context INTEGER := DBMS_LOB.DEFAULT_LANG_CTX;
  result       BLOB;
  warning      INTEGER;
  warning_msg  VARCHAR2(50);
BEGIN
  DBMS_LOB.CreateTemporary(
    lob_loc => result,
    cache   => TRUE
  );

  DBMS_LOB.CONVERTTOBLOB(
    dest_lob     => result,
    src_clob     => value,
    amount       => LENGTH( value ),
    dest_offset  => dest_offset,
    src_offset   => src_offset,
    blob_csid    => DBMS_LOB.DEFAULT_CSID,
    lang_context => lang_context,
    warning      => warning
  );

  INSERT INTO table_name ( xml ) VALUES ( result );
END;
/
1 rows affected

SELECT XMLQUERY(
         '/root/entry/string[1][text()="NAME2"]/../string[2]/text()'
         PASSING XMLTYPE( xml, NLS_CHARSET_ID('UTF8') )
         RETURNING CONTENT
       ) AS value
FROM   table_name;


VALUE


VALUE2


SELECT value
FROM   table_name
       CROSS APPLY XMLTABLE(
         '/root/entry/string[1][text()="NAME2"]/..'
         PASSING XMLTYPE( xml, NLS_CHARSET_ID('UTF8') )
         COLUMNS
           name  VARCHAR2(20) PATH './string[1]',
           value VARCHAR2(20) PATH './string[2]'
       );


VALUE


VALUE2


SELECT REGEXP_SUBSTR(
         TO_CLOB( xml ),
         '<entry>\s*<string>NAME2</string>\s*<string>([^<]*)</string>\s*</entry>',
         1,
         1,
         'c',
         1
       ) AS value
FROM   table_name


VALUE


NOT THIS