1. Method for processing a data cube for range-sum queries which includes a prefixed-sum cube to store the cumulative sum of data and a dynamic update cube using an index structure called &Dgr;-tree to store the updated values of the data cube comprising: storing the changes of the data cube into the &Dgr;-tree whenever the data cube changes, instead of updating directly to the prefixed-sum cube; and managing the changes of the data cube in the &Dgr;-tree.