GROUP BY all columns syntax
<p>In Oracle database, to specify one single group of all data </p>

<pre><code>SELECT sum(price)
FROM tabA
GROUP BY ()
</code></pre>

<p>I understand that <code>GROUP BY</code> clause can be omitted here, but if we include explicitly, would the full form be <code>GROUP BY ()</code> ? This is taken from <a href="https://docs.oracle.com/cd/B19306_01/server.102/b14223/aggreg.htm#i1006842" rel="nofollow">GROUPING SETS</a>'s documentation.</p>

<p>I remember reading once that <code>GROUP BY NULL</code> have the same meaning. Is it correct? Otherwise what would <code>GROUP BY NULL</code> mean ?</p>