Introduction to Database Systems

CHAPTER 8

QUERY PROCESSING AND OPTIMIZATION

After reading this chapter, the reader will understand:

• The steps involved in query processing
• How SQL queries are translated into relational algebra expressions
• The role of sort operation in database systems and the external sort–merge algorithm used for sorting
• Various algorithms for implementing the relational algebra operations such as select operation, project operation, join operation, set operations, and aggregate operations
• Two approaches of evaluating the expressions containing multiple operations, namely, materialized evaluation and pipelined evaluation
• Different types of query optimization techniques, namely, cost-based query optimization, heuristics-based query optimization, and semantic ...