How are null DB values handled when accessed via a query rule?

Question

Hello Everyone. How are null DB values handled when accessed via a query rule? When I use a query rule to retrieve a CDT the isnull() expression returns false on the single object even though the underlying table has null stored as the value. The field in question is of type Integer and Decimal and I'm running 6.6.1. Instead of isnull() I've actually had to resort to using the len() function on the value after casting it to a string.... 
 OriginalPostID-65941 
 OriginalPostID-65941

Tim · Accepted Answer

You're either answering your own question or maybe I'm mis-reading it.... If you RDBMS table has a row the result of isnull will be false even if the value is null in the row.