About the Talk
June 25, 2011 10:15 AM
University of Indianapolis, 1400 E Hanna Ave Indianapolis, INUniversity of Indianapolis, 1400 E Hanna Ave Indianapolis, IN
In this session we’ll look at the operations and transformations of relational algebra in order to understand how query plans are computed. Relational algebra represents the foundation of relational databases. Any valid SQL query is transformed after parsing into a parse tree in which the internal nodes are operators, leaves are relations (data sets) and subtrees are subexpressions. The primary goal of the query optimizer is to transform query trees into equivalent expression trees, where the average size of the resultsets yielded by subexpressions in the tree are smaller than they were before the optimization. The query optimizer uses a set of rules, to generate equivalent parse trees and then applies proportional costs for operators ...