This chapter describes the process by which queries are executed efficiently by a database system. The chapter starts off with measures of cost, then proceeds to al-gorithms for evaluation of relational algebra operators and expressions. | Chapter 13: Query Processing Aug 10, 2006 Database System Concepts, 5th Ed. ©Silberschatz, Korth and Sudarshan See for conditions on reuse Chapter 13: Query Processing s Overview s Measures of Query Cost s Selection Operation s Sorting s Join Operation s Other Operations s Evaluation of Expressions Database System Concepts 5th Edition. 13. ©Silberschatz, Korth and Sudarshan Basic Steps in Query Processing 1. Parsing and translation 2. Optimization 3. Evaluation Database System Concepts 5th Edition. 13. ©Silberschatz, Korth and Sudarshan Basic Steps in Query Processing (Cont.) s Parsing and translation q q translate the query into its internal form. This is then translated into relational algebra. Parser checks syntax, verifies relations s Evaluation q The queryexecution engine takes a queryevaluation plan, executes that plan, and returns the answers to the query. Database System Concepts 5th Edition. 13. ©Silberschatz, Korth and Sudarshan Basic Steps in Query Processing : Optimization s .
