Patent ID: 7010516

Claim:
A computer-implemented method for optimizing a database management system process of a query, the method comprising: collecting a plurality of single column statistics for a plurality of columns, the plurality of single column statistics providing estimates for row counts and unique entry counts for a single column operator; determining a first selectivity estimate as if the columns are substantially independent of each other; determining a second selectivity estimate as if the columns are substantially dependent on each other; determining a third selectivity estimate for predicates in the query using the first and second selectivity estimates, the third selectivity estimate being used in optimizing processing of the query by the database management system; wherein determining each of the first and second selectivity estimates comprises determining a cross product from the single column statistics; wherein determining the third selectivity comprises determining a measure of dependency between at least two columns; and wherein the third selectivity estimate is calculated based on the measure of dependency and a difference between the first and second selectivity estimates.