含空值关系数据库中关系代数的实现

本文从空值的完全语义出发,依据空值环境下信息等价和信息相容的含义,全面定义了空值环境下运算结果完备的关系代数运算,并对空值环境下关系代数运算的有效性和完备性进行了讨论。

In this paper, processing rules of relational algebra under null value circumstances are given on the meaning of equivalence and compatibity according to whole semantics of null value. Soundness and completeness of relational algebra art disscussed at the end of this paper.