关系数据库中“逻辑实体”的研究

Research of "Logical Entity" in Relational Database

在关系数据库中,物理表中的一行记录反映了现实世界中的某个对象,然而在实际应用中,有些对象需要由多行有相互联系的记录一起才能够完整的被反映,它们用传统方法不能很好地实现.针对此种情况提出了"逻辑实体"的概念,并给出了"逻辑实体"的数据结构、完整性约束、数据操作和具体实现,最后给出了具体的例子并与传统方法做了比较,分析了"逻辑实体"带来的优点.

In relational database, a row of record in the physical table reflects an object of the actual reality, but in practical application, some objects only can be completely reflected by several interrelated records, as they can not be implemented well by using traditional method. This paper presents the concept of ＂logical entity＂ according to this case , and give the data structure,integrity constraints,data operation and the implementation of ＂logical entity,＇. At last, it gives a specific example, as well as makes a comparison between the traditional method and the method on the basis of ＂logical entity＂ to analyze the merits which ＂logical entity＂ brings.