关系代数中除运算的分析应用及其SQL语句实现

Analysis and Application of Division Operation in Relational Algebra and the Implementation of Its SQL Statement

关系数据库系统使用关系数据模型组织数据,而关系模型是建立在集合代数的基础上,关系代数作为一种关系数据库操纵语言的传统表达方式,是以关系为运算对象的一组高级运算的集合。作为一种抽象的查询语言关系代数提供八种常用运算,以除运算最为复杂,在SQL中也没有专门的运算符来实现。通过对除运算原理及其应用分析和SQL语句实现的实践研究,从关系代数除运算的定义、实现思路、应用及SQL语句实现加以说明,在教学和实际应用方面均具有一定的指导意义。

Relational database system uses relational data model to organize data,and relational model is established on the basis of set algebra.As a traditional expression way of relational database manipulation language,relational algebra is a set of advanced operations with relational as the operational object.As an abstract query language,relational algebra provides eight kinds of common operations,among which the division operation is the most complex,and there is no special operator to realize in SQL.By studying the principle of division operation and its application analysis and the implementation of SQL statement,this paper illustrates the definition,implementation thinking,application and the implementation of SQL statement of the division operation of relational algebra,which has certain guiding significance in teaching and practical application..