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【判断题】
纸上得来终觉浅，绝知此事须躬行，说明实践是认识的来源。A.
正确
B.
错误
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反馈参考答案：
举一反三
【简答题】简述按采购权限不同的采购方式分类。
【简答题】简述采购绩效评估的分类。
【单选题】In the relational algebra θρ(r), ρ is called ( ).
A.
select operation
B.
rename
C.
project predicate
D.
selection predicate
【单选题】The symbol ρ is a ( ) operator in relational algebra.
A.
intersect
B.
select
C.
rename
D.
project
【单选题】Divisionis an additional operation in relational algebra, it can be replaced by which set of the following operations equivalently?
A.
Select, Project , Cartesian-Product
B.
Union, Project, Cartesian-Product
C.
Select, Rename, Cartesian-Product
D.
Set difference, Project, Cartesian-Product
【判断题】The operator ( ) associates every tuple of two tables in relational algebra.A. ∏ B. × C. θ D. ρ
A.
正确
B.
错误
【简答题】根据不同分类标准简述采购与供应的分类
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