更多"Let R and S be the relation respect"的相关试题:
[单项选择]Let R and S be the relation respectively:
Relation R: A B C Relation S: B C D
1 2 3 2 3 4
6 7 8 2 3 5
The number of tuplesthat the result of the expression R ∞ S (Here is the natural join of relations R and S) is
A. 3
B. 4
C. 6
D. 9
[单项选择]Suppose we have the relation schema R(A,B,C,D) with functional dependencies ;F{A→ B,B→C,C→D,D→A},then R(A,B,C,D) at least is in
A. 1NF
B. 2NF
C. 3NF
D. BCNF
[判断题]Let’s have a run through.This sentence means let’s run from one side to another.
[单项选择]For relation R where primary key contains multiple, no non-key attribute should be functionally dependent on a part of the primary key. This relation R is at least in
A. 1NF
B. 2NF
C. 3NF
D. BCNF
[单项选择]— Look, Mary looks sad．Let's go and ______．
— All right．
A. cheer up him
B. cheer him up
C. cheer up her
D. cheer her up
[单项选择]
Consider a relation R ( A，B，C，D ) with the following dependencies：
AB C, CD E, DE B.
A candidate key of this relation is （）.
A. AB
B. ABC
C. ABD
D. ABE
[单项选择]Let's have supper now.
[单项选择]Now let's stop talking and begin
[单项选择]Let's finish our homework in a few seconds; it's time we ______.
A. played football
B. will play football
C. play football
D. are playing football
[单项选择]"Let's go to the museum this afternoon. There's a wonderful exhibition." "OK. ______ we meet at the bus stop "
A. Will
B. Shall
C. Can
D. Should
[单项选择]The performances in relation to Whorf's claim of the Dani and the Piraha are______.
A. complementary
B. identical
C. similar
D. opposite
[单项选择]Let's be incredibly gracious and suppose that you know 1% of everything ________ to know.
A. it is
B. as is
C. there is
D. what is
