XPath and Databases

Consider a simple MySQL table created and loaded as follows:

CREATE TABLE x (doc VARCHAR(150));
INSERT INTO x VALUES ('
<book>
  <title>A guide to the SQL standard</title>
  <author>
    <initial>CJ</initial>
    <surname>Date</surname>
  </author>
</book> ');

INSERT INTO x VALUES ('
<book>
  <title>SQL:1999</title>
  <author>
    <initial>J</initial>
    <surname>Melton</surname>
  </author>
</book> ');