Introduction
Database management systems have become a benchmark tool for defending the computer user from aspects of secondary storage management. They are intended to develop the yield of application programmers and to make easy data access by computer-naive end users. There have been two key areas of research in database systems. One is the scrutiny of data models into which the real world can be mapped and on which interfaces for different user types can be built. Such conceptual models include the hierarchical, the network, the relational, and a number of semantics-oriented models that have been reviewed in a large number of books and surveys.
A second area of interest is the safe and efficient implementation of the DBMS. Computerized data have become a central resource of most organizations. Each implementation meant for production use must consider this by guaranteeing the safety of the data in the cases of concurrent access, recovery, and reorganization.
One major criticism of many early DBMS has been their lack of efficiency in handling the powerful operations they offer, particularly the content-based access to data by queries. Query optimization tries to solve this problem by integrating a large number of techniques and strategies, ranging from logical transformations of queries to the optimization of access paths and the storage of data on the file system level. Traditionally, each of these approaches has used a different language. This is probably one of the reasons why no comprehensive survey of query optimization techniques has yet been presented.
The intention of this research document is to re-examine query optimization methods in the common structure of relational calculus. According to Klug, a relational algebra demonstration is precisely comparable to it (2006) and according to Dayal et.al (2003), it is expandable to the network DBMS operation. The document also focuses on the difficulty of optimizing queries in the centralized Database management systems.
References
Dayal, U., and Goodman, N., (2003). “Query optimization for CODASYL database systems”. International Conference on Management of Data, New York, pp. 138-150.
Klug, A. (2006) “Calculating constraints on relational expressions”. ACM Trans. Database Syst. 5, 3 260-290.
