title: MySQL "NOT IN" not working
body: <p>Strange thing happening.  I am having a problem with my MySQL Community Server 5.1 installed on windows <strong><em>NOT IN</em></strong> query.  When I do this query:</p>
  
  <pre><code>select * 
    from table1 
    where date &gt;= "2012-01-01";
  </code></pre>
  
  <p>returns 582 rows</p>
  
  <pre><code>select * 
    from table1 
    where date &gt;= "2012-01-01" 
      and the_key in (select some_key from table2);
  </code></pre>
  
  <p>returns 15 rows</p>
  
  <p>so I would expect that the following query would return 582 - 15 = 567 rows</p>
  
  <pre><code>select * 
   from table1 
   where date &gt;= "2012-01-01" 
   and the_key not in (select some_key from table2);
  </code></pre>
  
  <p>returns 0 rows</p>
  
  <p>Why is this last query not returning any rows?</p>