Abstract: A method, apparatus, and article of manufacture for computing a plurality of order-based analysis functions for rows stored in a table in a computer system, wherein the table has a plurality of partitions. A determination is made concerning which of the order-based analysis functions have compatible order-specifications. The order-based analysis functions with the compatible order-specification are then performed simultaneously and in parallel against the partitions. Preferably, the computer system is a parallel processing database system, wherein each of its processing units manages a partition of the table, and the order-based analysis functions can be performed in parallel by the processing units.

Abstract: A stratified sampling mechanism is provided in a database system. The stratified sampling mechanism includes defining a clause in a query that indicates stratified sampling is desired. Data from a source table is stratified into different subgroups based on stratification conditions in the query. Sampling is performed within each subgroup.