【简答题】【消耗次数：1】
关系模式R∈1NF，若每一个决定因素都包含码，则称R∈[填空]。
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相关题目
【简答题】
若关系模式R∈1NF，且每一个非主属性完全函数依赖于码，则称R∈[填空]。
【单选题】
有关系模式R（U,F）∈1NF，若R中任意的非平凡的函数依赖X→Y，X中均包含码，则关系模式R的规范化程度至少为( )。
①
A．2NF
②
B．3NF
③
C．4NF
④
D．BCNF
【简答题】
有关系模式R(U,F)∈1NF，U=（A,B,C），若(A,B)→C，B→C，则该关系模式的规范化程度为[填空1]NF。
【简答题】
如果一个集合A上的二元关系R是[填空1]、[填空2]、[填空3]的，那么称R为A上的等价关系。
【单选题】
设R(U)是属性集U上的关系模式。X,Y是U的子集。若对于R(U)的任意一个可能的关系r，r中不可能存在两个元组在X上的属性值相等，而在Y上的属性值不等，则称（ ）。
①
Y函数依赖于X
②
Y对X完全函数依赖
③
X为U的候选码
④
R属于2NF
随机题目
【单选题】
In ____ recent years, Niagara Fallshave come to be appreciated more for their natural beauty as _______ wonder of nature.
①
the; a
②
the; the
③
/; the
④
/; a
【单选题】
He is ____, but his wife is _____.?
①
awake…asleep ?
②
awake…sleep ?
③
waking…asleep ?
④
wake…asleep ?
【单选题】
By the end of last month, she ____ over five hundred letters of congratulation from different parts of the world.
①
would received
②
has received
③
had received
④
receive
【单选题】
Mr. Downham asked the public their views on the two subjects currently ____ discussion.
①
with
②
at
③
to
④
under
【单选题】
People just say it out of politeness and they don’t really ____ it. ?
①
realize ?
②
mean ?
③
think ?
④
regard?
【单选题】
—Don’t forget to come to my birthday party tomorrow.—I ____ .
①
don’t
②
won’t
③
can’t
④
haven’t
【单选题】
Fortunately, Jack was only slightly injured in the traffic ____ .
①
incident
②
event
③
case
④
accident
【单选题】
I want to paint the wall, but I can’t ____ on the color. ?
①
design ?
②
decide ?
③
desire ?
④
detect?
【单选题】
The
book I ____ the other day can be found nowhere.
①
borrow
②
borrowed
③
are
borrowing
④
was
borrowing
【单选题】
Her parents objected to ____ that farmer, though he has a lot of money.?
①
her marrying ?
②
marrying ?
③
marry ?
④
her marrying with?