<p>What is an example of a fast SQL to get duplicates in datasets with hundreds of thousands of records. I typically use something like:</p>

<pre><code>SELECT afield1, afield2 FROM afile a 
WHERE 1 &lt; (SELECT count(afield1) FROM afile b WHERE a.afield1 = b.afield1);
</code></pre>

<p>But this is quite slow.</p>

This is the more direct way:
```
```
select afield1,count(afield1) from atable 
group by afield1 having count(afield1) > 1
```
```