摘要
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.
出处
《计算机应用与软件》
CSCD
1998年第1期1-9,58,共10页
Computer Applications and Software
关键词
关系数据库
空值
关系代数
有效性
数据库
Relational database, null value, relational algebra, soundness, completeness.
