| 空值和N关系代数 |
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| 引用本文： | 黎仁蔚. 空值和N关系代数[J]. 东南大学学报(自然科学版), 1986, 0(4) |
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| 作者姓名： | 黎仁蔚 |
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| 作者单位： | 南京工学院计算机科学与工程系 |
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| 摘 要： | 随着关系数据库理论与实践的发展,人们越来越注意到空值问题。本文引进了三种不同语义的空值,井在此基础上,讨论了空值对关系数据库的影响,给出了空值环境下的逻辑、集合和关系代数,还讨论了N关系代数的一些性质。 N关系代可用来作为处理数据库中空值问题的抽象数据查询语言。
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| 关 键 词： | 关系数据库 关系代数 集合和关系 多值逻辑 查询语言 |
Nulls and N-Relational Algebra |
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| Li Renwei. Nulls and N-Relational Algebra[J]. Journal of Southeast University(Natural Science Edition), 1986, 0(4) |
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| Authors: | Li Renwei |
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| Affiliation: | Li Renwei Department of Computer Science and Engineering |
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| Abstract: | The three semantically different nulls, which are inexisting value, existing but unknown value, and placeholder, in relational database are introduced, and a detailed discussion on N-logic, N-set and N-relational algebra is given as well. In addition, some of fundamenatal properties are proved. N-relational algebra we present can serve as an abstract data query language for an incomplete relational database. |
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| Keywords: | relational database relational algebra set and relation multivalued logic data query language. |
| 本文献已被 CNKI 等数据库收录！ |
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