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关系代数的五个基本操作是:并、差、_____、投影和选择。
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数据库系统原理(04735)
发表:2024年09月12日 01时09分44秒
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admin
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关系代数的五个基本操作是:并、差、_____、投影和选择。
【正确答案】:笛卡尔积
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Ted: What are you doing with all those books?
Pat: Trying to revise things for the exam tomorrow.
Ted: The last-night rush, you mean? _______
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American objected to that,and asked whether the proposed“direct payment'"were not really production subsidies in disguise.Officials on both sides were optimistic that a deal on farming,which would unlock
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