title: Aggregate function in where clause
body: <p>I have two tables:  TITLE and BACKGROUND</p>
  
  <p>BACKGROUND has a foreign key into TITLE so I'm trying to write a query that will return any TITLE rows that have more than one matching BACKGROUND.</p>
  
  <pre><code>SELECT T.ID
    FROM TITLE T, BACKGROUND B
   WHERE T.ID = B.TITLE_ID
     AND /* there are multiple matching background rows */
  </code></pre>