SQL: Combining sum and max aggregate function
<p>How do I get the max value from the following query:</p>

<pre><code>select sum(hours) from works_on group by pno;   
+------------+
| sum(hours) |
+------------+
|      52.50 |
|      50.00 |
|      55.00 |
|      25.00 |
|      55.00 |
+------------+
</code></pre>

<p>What I want is:</p>

<pre><code>|      55.00 |
|      55.00 |
</code></pre>

<p>Thanks in advance.</p>