create sequence seq_xdoc;
create table xdoc
(
  id integer not null default nextval('seq_xdoc'::regclass),
  xmldoc xml,
  primary key (id)
);

<?xml version="1.0" encoding="windows-1251" standalone="yes"?>
<!-- информация о сотруднике -->
<employee>
  <fio>
    <first_name>Иванов</first_name>
    <last_name>Иван</last_name>
    <second_name>Иванович</second_name>
  </fio>
  <post>доцент</post>
  <work_address>
    <postal-code>000000</postal-code>
    <city>Город</city>
    <street>ул. Советская</street>
    <house_number>00</house_number>
    <email>xxx@xxx.xx.xx<;/email>
    <telephone code="0-0000">00-00-00</telephone>
  </work_address>
</employee>

select xpath('//first_name/text()',xmldoc) from xdoc;
select xpath('/employee/fio/first_name/text()',xmldoc) from xdoc;

ОШИБКА:  could not parse XML document
DETAIL:  input conversion failed due to input error, bytes 0x98 0xD0 0xA1 0x3C
input conversion failed due to input error, bytes 0x98 0xD0 0xA1 0x3C
encoder error
line 9: Premature end of data in tag post line 9
  <post>доцент кафедры РњРћР