题目内容
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[主观题]
A、B、C三人合作搬运同样的两个仓库的货物，如果单独搬运一个仓库的货物，A需10小时，8需12小时，C
需要l5小时。A搬运甲仓库，8搬运乙仓库，同时开始搬运，C先帮助A搬运，中途又帮助8搬运，最后两个仓库同时搬运完。问：C帮助8搬运共用多少小时？()
A．3小时
B．4小时
C．5小时
D．6小时
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A．1NF
B．2NF
C．3NF
D．BCNF
更多“A、B、C三人合作搬运同样的两个仓库的货物，如果单独搬运一个…”相关的问题
第1题
For relation R where primary key contains multiple, no non-key attribute should be functio
nally dependent on a part of the primary key.This relation R is at least in
点击查看答案
第2题
For relation where primary key contains multiple attributes, no non-key attribute should b
e functionally dependent on a part of primary key. This relation R is at least in(66).
点击查看答案
A．3NF
B．2NF
C．INF
D．BCNF
第3题
For relation R where primary key contains multiple attributes,no non-key attribute should
be functionally dependent on a part of the primary key. This relation R is at least in
点击查看答案
A． 1NF
B．2NF
C．3NF
D．BCNF
第4题
For relation R where primary key contains multiple attributes,no non-key attribute should
be functionally dependent on a part of the primary key. This relation R is at least in
点击查看答案
A． 1NF
B．2NF
C．3NF
D．BCNF
第5题
If A is the primary key of relation R（A,B,C), then AC is：
A．primary key
B．candidate key
C．foreign key
D．supper key
第6题
请教：软件水平考试（初级）程序员上午（基础知识）模拟试卷2第1大题第54小题如何解答？
【题目描述】
For relation where primary key contains multiple attributes, no non-key attribute should be functionally dependent on a part of primary key. This relation R is at least in(66).A．3NF
B．2NF
C．INF
D．BCNF
| 【我提交的答案】： C |
| 【参考答案与解析】： 正确答案：A |
解析：译文：对于主键包含多个属性的关系，没有非主属性函数依赖于部分主键。这样的关系R至少是3NF。
【我的疑问】
为什么是3NF？不应该是2NF吗？他并没有说明是否有传递依赖关系。
第7题
Acandidate key is（).
A.an attribute or a set of attributes with a unique value for each tuple of a relation
B.a set of attributes referring to another relation in the database
C.an attribute or a set of attributes that is potentially the primary key of a relation
D.an attribute or a set of attributes that is potentially(有潜力地)the super key(超键)of a relation
第8题
The constraint “In a base relation, NO attribute of a primary key can be null”, is called :
A、Entity integrity
B、Referential integrity
C、Check constraint
D、User defined constraint
第9题
Which of the following conditions will make a relation that is in first normal form. to be
in second normal form？
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Ⅰ.every non-key attribute is functionally dependent on the full set of primary key attributes.
Ⅱ.no non-key attributes exist in the relation.
Ⅲ.the primary key consists of only one attribute.
A．Ⅰ only
B．Ⅰ and Ⅱ only
C．Ⅰ and Ⅲ only
D．any of them
第10题
A．PRIMARY KEY（仓库号)B．PRIMARY KEY（仓库号，商品号)C．PRIMARY KEY（商品号，地址)D．PRIMARY K
A．PRIMARY KEY(仓库号)
B．PRIMARY KEY(仓库号，商品号)
C．PRIMARY KEY(商品号，地址)
D．PRIMARY KEY(仓库号，地址)
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