关系数据库中关系模式的规范化

关系数据库中的关系模式直接影响了数据库中数据的完整性、准确性和一致性,好的关系模式能避免数据冗余和操作异常。关系规范化是设计关系模式的依据,是围绕函数依赖进行的。其基本思想是一个关系只描述一个主题,遵从"一事一地"原则,不能把彼此没有直接关联的属性放在一起,这将会导致关系数据库性能变坏。关系规范化过程是不断分解关系的过程。根据关系中属性间函数依赖情况规定了若干标准,这就是所谓的1NF、2NF和3NF,还有更高的范式,通常认为3NF在性能、扩展性和数据完整性方面都达到了最好的平衡,故一般关系模式设计要求达到3NF。

Standardization of Relation Pattern in Relation Data Base

The completeness, accuracy and compatibility concerning a pattern having had direct impact to the database middle data in relation database. A good relation Pattern will be able to avoid the data redundancy and abnormal handling. That relation normalizes is the pattern basis designing relation , it is dependent on progress around function. Whose fundamental thought is that a relation describes a subject only, follow "to be related distance of one"principle, it is can not direct put each other associative not attributes be in,this will be able to lead to the relation database function be changed into a dirty trick together. Concerning normalized process is the process breaking up relation unceasingly.Attribute room function be dependent on condition has stipulated some standards in basis relation,this has been called 1 NF,2 NF and 3 NF, has still had higher canonical form, has thought that 3 NF has all reached balancing best, reaching therefore the sort concerns pattern design call for 3 NF in the field of the function, extended and data completeness gen- erally.