The simplest parallel query optimization involves queries that access a single base table. Adaptive Server optimizes these queries by evaluating the base table to determine applicable access methods, and then applying cost functions to select the least costly plan.
Understanding how Adaptive Server optimizes single-table queries is integral to understanding more complex parallel queries. Although queries such as multitable joins and subqueries use additional optimization strategies, the process of accessing individual tables for those queries is the same.
The following example shows instances in which the optimizer uses parallel access methods on single-table queries.