title: Filtering on primary key with nullable column in cassandra versions 1.2.5 and greater
body: <p>Im trying to understand how to do this, or if I cant, why cant I do this. ie</p>
  
  <pre><code>cqlsh:ps&gt; create table s1 (a text, b text, stuff text, primary key(a,b));
  cqlsh:ps&gt; select * from s1 where a='a' and b=null;
  Bad Request: Invalid null clustering key part b
  </code></pre>
  
  <p>It appears that there is a work around, i.e. don't store nulls in column "b", but something like "##null##", but that just seems silly.</p>
  
  <p>Any help would be much appreciated.</p>