A computer is programmed to process a continuous query that is known to perform a new aggregation on one or more stream(s) of data, using one or more other aggregations on the stream(s). The computer creates an operator to execute the continuous query, and schedules the operator for execution in a specific order. In several embodiments, the computer determines the order based on dependency of the new aggregation on other aggregation(s), and on the order of performance of the other aggregation(s). The new aggregation is scheduled for performance after performance of each of the other aggregations. The computer is further programmed to pass results of the other aggregations to the new aggregation, by execution of a predetermined function. Support for use of the other aggregations results within the new aggregation eliminates redundant computation of the other aggregations within the new aggregation. The new aggregation may be user defined or built-in.