关于传统关系代数的说法，错误的是（ ~ ）。a.有m目x行数据的关系R和有n目y行数据的关系S进行笛卡尔积运算，其结果是有(m+n)目和(x+y)行数据的关系b.集合的并运算要求参与运算的两个关系必须具有相同的目c.对m目的关系R进行选择运算，其结果关系一定也是m目的 - 查题网

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国家开放大学 / 中华文化概说

关于传统关系代数的说法，错误的是（ ~ ）。

a.
有m目x行数据的关系R和有n目y行数据的关系S进行笛卡尔积运算，其结果是有(m+n)目和(x+y)行数据的关系

b.
集合的并运算要求参与运算的两个关系必须具有相同的目

c.
对m目的关系R进行选择运算，其结果关系一定也是m目的

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