摘要
范式是符合某一种级别的关系模式的集合。最基本的数据库范式有三个,第一范式(1NF),第二范式(2NF)和第三范式(3NF)。文章介绍了范式相关概念、1范式和2范式存在的问题和模式分解的方法。文章首先给出一个达到1范式的关系模式,分析里面存在的函数依赖,并分析了该模式存在的诸多问题。然后将此1范式分解为若干2范式。进而将2范式转换成若干3范式。通过模式分解在一定程度上解决了1NF存在的数据冗余大和插入异常、删除异常及其修改异常等问题。
Normal form is the set of relational mode suitable for a kind of level. Database to be built must abide by a certain rule. The most basic normal forms includes three kinds,namely 1NF, 2NF and 3NF. The related concepts of normal form, the problems of 1NF and 2NF and the ways of mode decomposition were introduced in this paper. In the first place, an example of 1NF was given. The functional dependency in the 1NF and the problems in it were listed. Then the 1NF was decomposed into several 2NF. Furthermore, a 2NF was decomposed into several 3NF. By means of mode decomposition, such problems as a lot of data redundancy, insertion anomalies, deletion anomalies and modification anomalies are dealt with to a certain extent.
出处
《价值工程》
2012年第26期213-214,共2页
Value Engineering
关键词
范式
规范化
函数依赖
模式分解
normal form
normalization
functional dependency
mode decomposition
