摘要
关系代数中的运算可分为基本运算和非基本运算 ,本文重点讨论了如何用基本运算表示非基本运算 ,给出了用基本运算表示除法运算的关系代数表达公式 ,解决了以往用抽象定义进行除法运算难度大的问题 ,直接应用除法的基本运算表达公式得出了结果 ,从而找到了在其它关系操作语言中进行与除法等价运算的一条重要途径。
The operations in relational algebra include basic operations and additional operations. This article mainly discusses the method how to express additional operations with basic operations, especially an expression is given to express the division operation. It solves the problem that division operation is done by using abstract definition, the with the given expression the division result can be directly obtained. It is an important way to do equivalence division operation in other relational operation languages.
出处
《陕西科技大学学报（自然科学版）》
2003年第1期89-92,共4页
Journal of Shaanxi University of Science & Technology
关键词
关系代数
非基本运算
基本运算
除法运算
relational algebra
fundamental operations
additional operations
division operation
