<company>
    <department>
        <name>Marketing</name>
        <emps>
            <employee id = "201">
                <first_name>Michael</first_name>
            </employee>
            <employee id = "202">
                <first_name>Pat</first_name>
            </employee>
        </emps>
    </department>
    <department>
        <name>Accounting</name>
        <emps>
            <employee id = "205">
                <first_name>Shelley</first_name>
            </employee>
            <employee id = "206">
                <first_name>William</first_name>
            </employee>
        </emps>
    </department>
</company>

I believe that SQLXML should work in 9i and 10g but not 8i.

Oh! by the way, the backslashes are added by Markdown. I tried, but I could not get rid of them. Sometimes Markdown is bad

select  xmlelement ("company",
           xmlagg (xmlelement ("department",
           xmlelement ("name", dept.department_name),
           xmlelement ("emps",
             (select xmlagg (xmlelement ("employee",
               xmlattributes (emp.employee_id as "id"),
               xmlforest (emp.first_name as "first_name")))
             from    employees emp
             where emp.department_id = dept.department_id)
                       )
                   )
           )
       ) xml
from departments dept