Query Optimization Part 1

This presentation discusses the fundamentals of the DB2 query optimization techniques. Part 1 gives an overview of the basic SQL constructs and explains their impact on query performance. The DB2 runtime architecture and impact of predicate evaluation order and timing are described. The presentation also gives an introduction to the basic optimization algorithm. Part 2 discusses query transformation, including techniques that DB2 employs and how these transformation techniques impact query performance. An overview of cost estimation of access paths is included. Finally, the presentation explains how data statistics can impact the optimal access path that DB2 selects.