title: Every derived table must have its own alias error
body: <p>I get that error when running the following query:</p>
  
  <pre><code>SELECT MAX( DateTime )
  FROM (
  (
      SELECT DateTime
      FROM Class_Searches
  )
  UNION ALL (
      SELECT DateTime
      FROM Book_Searches
  )
  )
  WHERE User_Email = 'bla@blah.com'
  AND DateTime &gt; NOW( ) - INTERVAL 30 DAY 
  </code></pre>
  
  <p>I know I need to add Aliases but I'm not sure where</p>