Query transformation in an instructional database management system
Bogdan Czejdo, Marek Rusinkiewioz · 1984
A database management system designed for instructional use should offer facilities usually not required in a commercial environment. One of the most important features desirable in such a system is its ability to perform query transformation. The use of an universal symbol and tree manipulation system to perform query translation, decomposition and optimization is described in the paper. Examples of transformation rules required to translate SQL expressions into equivalent QUEL expressions, decompose SQL expressions into parse trees and perform optimization of expressions based on relational algebra are shown.