Methods for parallel query execution of a database operation on a database utilizing a graphics processing unit (GPU) are presented including: receiving query by a host, the query including database relations; starting a GPU kernel, where the GPU kernels include a GPU memory; hash partitioning the database relations by the GPU kernel; loading the partitioned database relations into the GPU memory; loading keyed partitions corresponding the hash partitioned database relations into the GPU memory; building a hash table for a smaller of the hash partitioned database relations; and executing the query. In some embodiments, methods further include returning a result of the query. In some embodiments, methods further include when the query is a long query including a number of operators, parsing the long query into a number of sub-queries; for each of the sub-queries, starting one of the GPU kernels such that the sub-queries are processed in parallel.