This paper deals with the semantics of null values in functional dependencies in database theory, and presents three different definitions of FDs in a single relation with marked nulls.
本文研究关系数据库理论中空值在函数依赖中的语义问题，提出了带标志空值的关系中函数依赖的三种定义。
Three Top-Down color design mode were proposed. They are each based on freely matching colors, color harmony theory and concept color scheme database.
提出了基于自由配色、基于色彩调和理论和基于概念色彩方案库的三种自顶向下色彩设计模式。
应用推荐