<command>DISTINCT ON <replaceable class="PARAMETER">column</replaceable></command> will eliminate all duplicates in the specified column; this is
equivalent to using <command>GROUP BY <replaceable class="PARAMETER">column</replaceable></command>. <command>ALL</command> will return all candidate rows,
including duplicates.
including duplicates.</para>
<para>
The GROUP BY clause allows a user to divide a table