According to the docs for the fetchColumn() method in the abstract Zend_Db_Statement, it will return a value, or false if there is no value to return.

All child classes either inherit this method, or if they override it (eg. in Zend_Db_Statement_Pdo), they retain the same behaviour: If there are no more rows in the result set, return FALSE.

However, Zend_Db_Statement_Oracle behaves differently. If there are no more rows in the result set, it throws a Zend_Db_Statement_Oracle_Exception. This inconsistency makes it impossible to write code that is database-independent.

The problem also affects Adapter::fetchOne(), which internally calls Statement::fetchColumn() to do its work.