摘要
允许含有空值的关系模式是建立新型的不完全信息数据库的基础。为了进一步讨论这类模式的分解等一系列问题,至少要对空值环境下的函数依赖集的最小覆盖问题进行深入研究。本文讨论了这一问题,并且提出了空值环境下满足数据保持条件的函数依赖集最小覆盖的求法,为允许含有空值的关系模式的进一步研究准备了条件。
The relational schema that is permited to have null value is the basis of setting up in-
complete information database.In order to further discuss the problems such as decomposing of this
kind of relational schema,we have to reserch deeply about minimal cover problem for set of func-
tional dependancy under null value circumstances at least.We discuss the problem in this paper,also
we give out a solution of solving minimal cover of functional dependency set that satisfied data ho-
lding conditions under null value circumstance,so prepared the condition for the deeply reserching of
the relational schema that is permited to have null value.
出处
《计算机研究与发展》
EI
CSCD
北大核心
1991年第8期10-15,共6页
Journal of Computer Research and Development
