ABSTRACT

The SQL language allows users to express the queries that have nested sub-queries in them. Optimization of nested queries has received considerable attention over the last few years. Most of the previous optimization work has assumed that at most one block is nested within any given block. The two main contributions of this report are: 1. Optimization strategies for queries that have an arbitrary number of blocks nested within any given block, and 2. a new algorithm for the execution of nested queries, involving one or more other joins, in a multi-processor environment. The new algorithm cuts down the processing costs over conventional algorithms.