title: How can I filter a table using an aggregate condition?
body: <p>I have a simple table of 10 customers with ID, Name and Age.
  How can I filter this so that I only select Customers with Age &gt; 30?
  I tried the HAVING clause but keep running into problems.</p>
  <p>Thanks in advance.</p>
  <p>Here's my code below:
  My Code below:</p>
  <pre><code>SELECT *
  FROM Customer_Table
  HAVING Age &gt; AVG(AGE)
  </code></pre>