title: Select count for a date range where the data is NOT IN the rest of the table
body: <p>This is what I have...</p>
  
  <pre><code>SELECT COUNT(DISTINCT customer_number)
  FROM   leads
  WHERE  ( dealer_id = '75'
            OR dealer_id = '76'
            OR dealer_id = '77'
            OR dealer_id = '78'
            OR dealer_id = '70'
            OR dealer_id = '2692'
            OR dealer_id = '2693' )
         AND date BETWEEN '2013-04-01' AND '2013-04-06'
         AND customer_number NOT IN (SELECT customer_number
                                     FROM   leads
                                     WHERE  date &lt; '2013-04-01')  
  </code></pre>
  
  <p>I basically just need to do a select count where the customer_number is only counted once between the date range but also that the customer_number is not in the rest of the table.</p>
  
  <p>The query above just returns zero.</p>