空值环境下嵌入多值依赖的研究
Research on Embedded Multivalued Dependency Under Null Value Circumstances
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摘要: 本文深入讨论了空值环境下的满足强、弱保持的嵌入多值依赖的概念，给出了嵌入多值依赖的投影规则及ＮＭＶＤ：Ｘ→→Ｚ强保持成立的充要条件，证明了近投影性定理。Abstract: In this paper,The multivalued dependency concepts to satisfy strong and weak holding are discussed to make NMVD:X→→Z strong holding hold water and the inverse projection theorem is proved
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