title: Handling Null in Greatest function in Oracle
body: <p>I want to compare two dates from two columns and get the greatest and then compare against a date value.
  The two column can hold NULL values too.</p>
  <p>For example I want the below OUTPUT.</p>
  <pre><code>Col A         Col  B          OUTPUT
  ---------------------------------------
   NULL          NULL            NULL
   09/21/2013    01/02/2012      09/21/2013
   NULL          01/03/2013      01/03/2013 
   01/03/2013    NULL            01/03/2013 
  </code></pre>
  <p>How do I use the greatest function or if there is anything else?
  I am again using the output to compare against another date.</p>