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若一个关系的元组个数是无限的，则称这个关系为( )，否则称为( )，关系数据库考虑的是( )。
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一个关系中属性个数为l时称此关系为
对应关系
单一关系
一元关系
二元关系
一个关系中属性个数为1时称此关系为
对应关系
单一关系
一元关系
二元关系
在一个关系的若干个候选码中指定一个用来唯一标识该关系的元组则称这个被指定的候选码为该关系的
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