【摘要】 本文首先给出了空值环境下基于3值逻辑的比较运算的处理规则，之后以参考文献[1]中含空值关系数据库关系代数的处理策略为基础，深入研究了空值环境下基本关系代数运算同其它关系代数运算之间的关系，验证了空值环境下基本关系代数是关系代数中的最小完备集。更多还原

【Abstract】 In this paper, processing rulers of comparative calcutation are given on the basis of 3 valued logic under null value circumstance, and the relationship between foundational operations in relational algebra and other relational algebra are deeply researched under null value citcumstance on the basis of processing policy of relational algebra in literature [1]. It is tested and verthed that the foundational operations in relational algebra is the minimal complete set in relational ateebra under null vaiue circumstance.更多还原