title: how do I query for rows that are missing a value?
body: <p>Got a column family that looks like: </p>
  
  <pre><code>CREATE TABLE data (
    id uuid,
    order_id text,
    order_ts timestamp,
    product_category text,
    product_distributor text,
    store_state text,
    transaction_discount decimal,
    transaction_id text,
    transaction_qty int,
    transaction_total decimal,
    PRIMARY KEY (id)
  ) 
  </code></pre>
  
  <p>How do I query all rows that don't have <code>transaction_total</code>? Seems like it'd be simple (<code>ISNULL</code>) but that doesn't exist in Cassandra. </p>