An improved approach is described for handling parallelization of window functions, particularly window functions that do not contain partition keys or which has low cardinality for the partition keys. The approach is highly scalable and can be used to greatly improve query processing. A two stage evaluation approach is employed to parallelize the processing of window functions. In the first stage, which is highly parallel, the majority of the computation of window function is done by all available processes. In this way, the entire computing power of the database server is utilized. The second stage, which is serial but is likely to be very short, all processes involved in first stage synchronize and complete the window function evaluation.