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【判断题】
淌自己的汗,吃自己的饭,自己的事自己干。靠天靠人靠祖宗,也是好汉。
A.
正确
B.
错误
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举一反三
【单选题】The symbol means ( ) NOT in relational algebra.∧
A.
∧
B.
￢
C.
∨
D.
∏
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【简答题】简述按采购权限不同的采购方式分类。
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【单选题】下列哪一项最可能导致生产可能性曲线向外移动（）
A.
消费品生产增加，资本品生产减少
B.
有用性资源增加或技术进步
C.
通货膨胀
D.
失业
查看完整题目与答案
【单选题】In the relational algebra θρ(r), ρ is called ( ).
A.
select operation
B.
rename
C.
project predicate
D.
selection predicate
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【单选题】下列哪项最可能导致DNA变性( )
A.
加入巯基乙醇
B.
加入甲酰胺及尿素
C.
搅拌
D.
磷酸二酯键的断裂
E.
丙酮
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【单选题】The symbol ρ is a ( ) operator in relational algebra.
A.
intersect
B.
select
C.
rename
D.
project
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【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
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【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
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【单选题】Natural join is an additional operation in relational algebra, it can be replaced by which set of the following operations equivalently :
A.
Select, Project
B.
Cartesian-Product, Project
C.
Cartesian-Product, Select, Project
D.
Cartesian-Product, Select
查看完整题目与答案
【简答题】根据不同分类标准简述采购与供应的分类
查看完整题目与答案
相关题目：
【单选题】The symbol means ( ) NOT in relational algebra.∧
A.
∧
B.
￢
C.
∨
D.
∏
查看完整题目与答案
【简答题】简述按采购权限不同的采购方式分类。
查看完整题目与答案
【单选题】下列哪一项最可能导致生产可能性曲线向外移动（）
A.
消费品生产增加，资本品生产减少
B.
有用性资源增加或技术进步
C.
通货膨胀
D.
失业
查看完整题目与答案
【单选题】In the relational algebra θρ(r), ρ is called ( ).
A.
select operation
B.
rename
C.
project predicate
D.
selection predicate
查看完整题目与答案
【单选题】下列哪项最可能导致DNA变性( )
A.
加入巯基乙醇
B.
加入甲酰胺及尿素
C.
搅拌
D.
磷酸二酯键的断裂
E.
丙酮
查看完整题目与答案
【单选题】The symbol ρ is a ( ) operator in relational algebra.
A.
intersect
B.
select
C.
rename
D.
project
查看完整题目与答案
【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
查看完整题目与答案
【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
查看完整题目与答案
【单选题】Natural join is an additional operation in relational algebra, it can be replaced by which set of the following operations equivalently :
A.
Select, Project
B.
Cartesian-Product, Project
C.
Cartesian-Product, Select, Project
D.
Cartesian-Product, Select
查看完整题目与答案
【简答题】根据不同分类标准简述采购与供应的分类
查看完整题目与答案