【判断题】【消耗次数：1】
在关系R(U)中，若X->Y，且Y->Z，那么X->Z就是传递函数依赖。
①
正确
②
错误
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相关题目
【单选题】
已知if (xy||xz);z=x; x=y; y=z;int x=30,y=50,z=80;语句执行后变量x、y、z的值分别为：。
①
x=50, y=80, z=80
②
x=50, y=30, z=30
③
x=30, y=50, z=80
④
x=80, y=30, z=50
【单选题】
已知 int x=30,y=50,z=80;以下语句执行后变量x、y、z的值分别为：。if (xy||xz)z=x; x=y; y=z;
①
x=50, y=80, z=80
②
x=80, y=30, z=50
③
x=30, y=50, z=80
④
x=50, y=30, z=30
【单选题】
已知 int x=30,y=50,z=80;以下语句执行后变量x、y、z的值分别为：。if (xy||xz)z=x; x=y; y=z;
①
x=50, y=80, z=80
②
x=50, y=30, z=30
③
x=30, y=50, z=80
④
x=80, y=30, z=50
【单选题】
在关系模式R中，函数依赖X→Y的语义是( )。
①
在R的某一关系中，若任意两个元组的X值相等，则Y值也相等
②
在R的一切可能关系中，若任意两个元组的X值相等，则Y值也相等
③
在R的某一关系中，Y值应与X值相等
④
在R的一切可能关系中，Y值应与X值相等
【判断题】
公式“x$y(F(x, y) ù G(y, z)) ú $xH(x, y, z)”中的全称量词x的辖域为：$y(F(x, y) ù G(y, z)) 。
①
正确
②
错误
随机题目
【单选题】
11.It was getting dark. I found a car____in a pool by the side of the road.
①
to be stuck
②
stuck
③
sticking
④
stick
【单选题】
11.Mrs. Black has got ____ instead of getting any better.
①
more bad
②
a little worse
③
much badly
④
a lot of worse
【单选题】
2. When we speak to people, we should be ___.
①
as polite as possible
②
as polite as possibly
③
as politely as possible
④
as politely as possibly
【单选题】
16. The jacket was so ____ that he decided to buy it.
①
much
②
little
③
expensive
④
cheap
【单选题】
19. Your room is ____ mine.
①
twice as large
②
twice the size of
③
bigger twice than
④
as twice large as
【单选题】
4. I think the story is not so ____as that one.
①
interesting
②
interested
③
more interesting
④
most interesting
【单选题】
3.This book is ____that one, but ____than that one.
①
as difficult as; expensive
②
as more difficult as; more expensive
③
as difficult as; more expensive
④
more difficult as; as expensive