基于关系模型的含空值关系数据库的数据更新

Updating the Data in Relational Databases Containing Null Value Under Relational Model

本文以空值的完全语义为基础，以空值环境下基于５值（５ＶＬ）的选择运算为工具。

In this paper,on the basis of the whole semantics of null value,we study the data update policy containing null value under relational mode in detail, using the selection operation which is based on five valued logic in null value environment.