A method, system and computer program product for operating a database includes: receiving a query including a first component indicating a criteria for generating a materialized query table (MQT) from the database and a second component having a condition for generating a reference value indicating a state of one or more items in the database; generating the MQT from the database where the MQT includes data items satisfying the criteria; generating, by executing the second component in response to receiving the query, a first reference value; receiving, subsequent to generating the first reference value, a second query for retrieving a data item from the MQT; generating, by executing the second component in response to receiving the second query, a second reference value; determining whether the first and second reference values are equal; and updating the MQT when the first reference value is not equal to the second reference value.