Let R and S be the following relations:
A.3
B.4
C.5
D.6
第1题:
A. followed,followed
B. followed,following
C. following,followed
D. following,following
第2题:
若 R = {(a,b), (b,a), (c,a)} 及 S={(a,a), (b,b), (c,a), (a,c)} 是两个关系,则 S◦R 中包含()个有序二元组。
A.3
B.4
C.5
D.6
第3题:
设有关系R(A,B,C)和S(B,C,D),则R∞S的属性个数是
A.3
B.4
C.5
D.6
第4题:
A.look at
B.look up
C.look for
D.look around
第5题:
47、设有关系R(A,B,C)和S(B,C,D),则R∞S的属性个数是
A.3
B.4
C.5
D.6
第6题:
10、Let's ________________(保持联络).