ass="title" style="clear: both">3.5. Window Functions <a href="#TUTORIAL-WINDOW" class="id_link">#</a></h2></div></div></div><a id="id-1.4.5.6.2" class="indexterm"></a><p>
    A <em class="firstterm">window function</em> performs a calculation across a set of
    table rows that are somehow related to the current row.  This is comparable
    to the type of calculation that can be done with an aggregate function.
    However, window functions do not cause rows to become grouped into a single
    output row 