UPDATE subquery nested in SELECT query
<p>I was wondering what the rules for subqueries exactly are.</p>

<p>For example:</p>

<ol>
<li>can we nest any query statement inside any other statement?</li>
</ol>

<p>(e.g. an UPDATE query inside an INSERT query... I know it really does not make any sense, ut I was looking at SQL injections and I was wondering if it could work...)</p>

<ol start="2">
<li>Does nesting only works in precise zones of the SQL code? (e.g. after WHERE clause)</li>
</ol>

<p>I tried a search but didn't found nothing exhaustive on the web.</p>