like non-window aggregate calls would.  Instead, the
    rows retain their separate identities.  Behind the scenes, the window
    function is able to access more than just the current row of the query
    result.
   </p><p>
    Here is an example that shows how to compare each employee's salary
    with the average salary in his or her department:

</p><pre class="programlisting">
SELECT depname, empno, salary, avg(salary) OVER (PARTITION BY depname) FROM empsalary;
</pre><p>

</p><pre class="screen">
  de