›› 2010, Vol. 23 ›› Issue (12): 99-101.

• 论文 • 上一篇    下一篇

模式分解保持函数依赖的意义

于思江,王小兵   

  1. (1.西安邮电学院 教务处,陕西 西安〓710121;2.西安电子科技大学 计算机学院,陕西 西安〓710071)
  • 出版日期:2010-12-15 发布日期:2010-12-30
  • 作者简介:于思江(1981-),女,工程师。研究方向:数据库理论。王小兵(1979-),男,讲师,博士。研究方向:数据库理论。

Significance of Preservation of Functional Dependencies in Schema Decompositions

 YU Si-Jiang, WANG Xiao-Bing   

  1. (1.Educational Administration Section,Xi'an Institute of Posts and Telecommunications,Xi'an 710061,China;
    2.School of Computer Science,Xidian University,Xi'an 710071,China)
  • Online:2010-12-15 Published:2010-12-30

摘要:

规范化过程通过模式分解提高关系的范式级别,分解的评判准则是无损连接性和保持函数依赖。文中证明了保持函数依赖的一个定理,说明了模式分解保持函数依赖的意义是在减小数据冗余度的同时不会影响数据更新的性能,通过具体分析实例进一步说明了该结论。

关键词: 规范化, 模式分解, 保持函数依赖

Abstract:

Normalization can improve the normal form degree of relations through schema decompositions,and the criteria are lossless join and preservation of functional dependencies.A theorem on preservation of functional dependencies is proved,and it is shown that the significance of preservation of functional dependencies do not affect the performance of data updates while reducing data redundancy.The concrete analysis of an example further confirms the conclusion.

Key words: normalization;schema decomposition;preservation of functional dependencies

中图分类号: 

  • TP311