| 改进的空值环境下扩展关系模型及其基本运算 |
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| 引用本文： | 叶仰明. 改进的空值环境下扩展关系模型及其基本运算[J]. 厦门大学学报(自然科学版), 1996, 35(6): 847-852 |
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| 作者姓名： | 叶仰明 |
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| 摘 要： | 用集合论的方法定义一个空值环境下的改进扩展关系模型及其基本运算，改进了文［１］的扩展关系模型．
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| 关 键 词： | 空值，扩展关系模型，基本运算，选择，集合差 |
An Improved Extended Relational Model Under Null Values Circumstances and its Fundamental Operations |
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| Ye Yangming. An Improved Extended Relational Model Under Null Values Circumstances and its Fundamental Operations[J]. Journal of Xiamen University(Natural Science), 1996, 35(6): 847-852 |
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| Authors: | Ye Yangming |
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| Affiliation: | Dept. of Compu. Sci. |
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| Abstract: | In this paper, we define an improved extended relational model under null values circumstances and its fundamental operations by using set theory. It improves the extended relational model of the papar[1]. |
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| Keywords: | Null values Extended relational model Fundamental operations selection Set difference |
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