n is scanned
        once for every row found in the left relation. This strategy
        is easy to implement but can be very time consuming.  (However,
        if the right relation can be scanned with an index scan, this can
        be a good strategy.  It is possible to use values from the current
        row of the left relation as keys for the index scan of the right.)
       </p></li><li class="listitem"><p>
        <em class="firstterm">merge join</em>: Each relation is sorted on the join
        at