1. A method for executing a database query in a computer system, comprising the computer-executed steps of: automatically selecting one or more candidate partitions of a partitioned database table for determining separate query execution strategies to be used for evaluating said database query, said partitioned database table having multiple previously defined partitions, each partition having a common definitional structure and comprising a respective disjoint subset of records of said partitioned database table, said candidate partitions comprising at least one and fewer than all previously defined partitions of said partitioned database table, said automatically selecting one or more candidate partitions step being performed without determining whether execution of said database query can benefit from using a separate query execution strategy for evaluating said database query against any said previously defined partition; wherein said step of automatically selecting one or more candidate partitions of a partitioned database table comprises using at least one criterion from the set of criteria consisting of: (a) at least one parameter indicating the existence of at least one local index for a partition of said database table; (b) at least one parameter indicating volatility of a partition of said database table; and (c) at least one parameter indicating a relative size of a partition of said database table; and responsive to automatically selecting one or more candidate partitions of a partitioned database table, automatically generating a respective separate query execution strategy for evaluating said database query against each candidate partition of said candidate partitions of said partitioned database table, and automatically generating a union of a respective results set of each said separate query execution strategy, to execute more efficiently than a common query execution strategy for evaluating said database query against all partitions of said partitioned database table.