Research Of Database Normal Form Decomposition

Database technology is the most rapidly developing one of the key areas of the computer and information science ,Its applications and research area is being enlarged, and become important tool of developing all kinds of information systems. Its widespread use has made computer application depth in all spheres of society. Database system's basic principles and application of technology have become the essential knowledge and skills for the science and engineering students.Relational database is main stream database, which is related to the relational model. With relational model as a basis, we can design a relational database. Relational database design goal is to generate a set of relation schema, which make we not need to store unnecessary duplication and facilitate access to the information. One option is to design schemas which meet the appropriate normal form. Through decomposing non-normalization of schema to correlative normal form, we can get normalization relational schemas, which can make us design a good database, therefore, the profound understanding of normal form decomposition is crucial. In this paper we only discuss two important normal form—BCNF and 3NF, we will use software to inplement normal form decomposition and describe its implementation process.This article describes the database firstly; then introduces the relational database and the Decomposition theory of normal form based on the relational database relational database paradigm based on the theory of decomposition; thirdly, introduces the related algorithms; at last ,introduces the study and the process implementation about the relational database decomposition of normal form. According to research and analysis, the main problem should be resolved of this subject is: turning Algorithm and Pseudo-code Into application programming language; completing the research of visualization software of relational database normal form decomposition; well and friendly designing on the interface ;combination between decomposition algorithm and interface. Preliminary work is to find relevant information, familiar the development environment of the VC, demonstrate the feasibility of the system, complete the topic starting report. The latter work is mainly about writing code and system debugging and improvement, he main system is divided into seven modules: closure solution of attribute set, closure solution of Function dependency set, solution of Regular coverage, solution of super key , solution Candidate of Code, decomposition of BCNF normal form and decomposition of 3NF normal form. The system uses object-oriented methods, using Iterative, incremental Development model, using class to communicate between these modules , to achieve low coupling, high cohesion.The program consists of two main modules, as well as five sub-modules. The two main modules is BCNF decomposition and 3NF decomposition. The five sub-modules is computing closure of attribute sets, computing closure of a set of functional dependencies, computing canonical cover, computing candidate key and computing super key. We will Particular describe the design, also with the activity diagram explaining. The system is coded in Visual C++.In this paper, the specific structure is as follows:ChapterⅠ—IntroductionA summary description about the Origin of normal form decomposition and a brief description of its role. briefly introduce about the importance of visual decomposition research and implementation based on relational database. Finally, a simple introduction to the main work of this article.ChapterⅡ-----normal form decomposition theory of relational databaseFirst of all, the introduction of database and relational database, then explaining the theory in detail including functional dependency, closure of functional dependency set, closure of attributes set , Regular coverage, pattern Decomposition , Boyce -Codd Normal Form, the third Normal Form paradigm. Then Comparative analysis about BCNF and 3NF, Finally, introduction about the other normal form and their application and research.ChapterⅢ-----relevant knowledge and technologyFirst introduced algorithm about BCNF and third normal form, furthermore Analysis these algorithm briefly, including power set Algorithm, Solution Algorithm of attributes set closure , Solution Algorithm of function-dependent set closure , Solution Algorithm of Regular coverage, BCNF decomposition , Solution Algorithm of super key and candidate code, decomposition Algorithm of the third normal form. Then, normal form Followed by a brief introduction of Visual C++ development environment. Finally, explain the object-oriented programming technique.ChapterⅣ------the design and implementation of normal form decompositionprogramFirst of all, introduced the design process, the procedure of the main program includes: Calculation Module of attributes closure set, Calculation Module of function-dependent set closure, decomposition Module of BCNF, solution Module of Regular coverage, Calculation Module of super key, Calculation Module of candidate code, decomposition Module of the third normal form. And then focuses on the major class categories of this program, describing the CArithmeticKernel class and CBcnfDecompDialog class in detail, and the rest of the class in brief.CArithmeticKernel which is the class of algorithms, all functions based on algorithms are in it, introducing the function with a detailed description and result analysis, and a further description with little program for some part.ChapterⅤ-----Summary and prospectIn order to let database design approaching a comprehensive, Peoples make a study of standardization theory, which is to use normal form to design database. In 1971, E.F.Codd put on the standardization theory of normal form. At present, the theory research has come a long way. The standardization theory is an important theoretical basis for relational database, it guides the design of relational database or relational pattern. And the current data pattern is relational database pattern, many commercial databases are also based on the relational data pattern, such as Oracle, DB2, SQL SERVER. Therefore, understanding deeply in normal form decomposition is essential, but we cannot see any soft practice with normal form decomposition. Hoping to help the learners well understanding relational database and mastering the Methods to design relational database ,by research of normal form decomposition. The subject of study has been completed, better accomplishing in BCNF decomposition and third normal form. Furthermore, expanding the capability with five Module : Solution Algorithm of attributes set closure , Solution Algorithm of function-dependent set closure, Solution Algorithm of Regular coverage, Solution Algorithm of super key and candidate code. The vast majority of models can be decomposed . because the less restriction, sometimes it may not work correctly that should improve in future.