关系数据库二三范式判别算法

Determination Algorithms for 2NF and 3NF

第二范式(2NF)和第三范式(3NF)在关系数据库规范化中起着重要作用。然而,所有的文献都没有给出第二、三范式的判别算法,当关系模式属性较多或数据依赖较复杂时,很难通过手算做出正确的判断。本文首先给出判别给定属性集是否键码的算法以及求给定关系模式的所有键码和所有非主属性的算法,然后在简单刻划函数依赖特征的基础上提出2NF和3NF的判别算法。这些算法与现有文献上的各种算法一起便于在计算机上编程实现,从而使关系规范化理论变成应用软件。

2NF and 3NF take an important part in normalization of relation database. Whereas no corresponding algorithms have been given, it is difficult to determine them manually in case of many attributes or complicated data dependency. In this paper determination algorithms for 2NF and 3Nf are presented on the basis of a simple characterization of them with an advance statement of a distinguishing algorithm of keys and an algorithm of finding all the keys and nonprime attributes of a relation pattern. These algorithms in company with the others in existing references are convenient for the software realization of normalization theory of relation database.