1. A method for a refreshing a materialized query table (MQT) in a database, the method comprising the steps of: parsing a query to identify a database table with a MQT in deferred maintenance; determining whether to update the MQT in deferred maintenance to execute the query by performing the steps of: estimating a time to execute the query over a base table corresponding to the MQT in deferred maintenance; estimating a time to update the MQT in deferred maintenance; comparing the estimated time to update the MQT in deferred maintenance and the estimated time to execute the query over the base tables; updating the MQT in deferred maintenance where the estimated time to update the MQT is less than the time to execute the query; and executing the query over the now updated MQT in deferred maintenance.