TheAustraliansareliketheEnglishinmanywaystheyhavemanyBritishrelatives.()A.ifB.becauseC.soD.although
The Australians are like the English in many ways_____they have many British relatives.( )
A. if
B. because
C. so
D. although
设有关系R(A,B,C) 和S(A,D,E,F),若将关系代数表达式: JIR.A,R.B,S.D, 2020-05-23 …
设关系R、s和T分别如下图所示,其中T是R和S的一种操作结果。则A.T=R ∞SB.T=R∞SC<E 2020-05-23 …
有关系R(A, B, C) 和关系S(A, D, E, F)。如果将关系代数表达式πR.A, R.B 2020-05-23 …
设有关系R(A,B,C)和S(A,D,E,F),若将关系代数表达式:∩R.A,R.B,S.D,S.F 2020-05-23 …
设有关系R(A,B,C) 和S(A,D,E,F),若将关系代数表达式:∏R.A,R,R.B,S.D, 2020-05-23 …
关系R(A,B,C)和S(A,D,E,F),有R.A=S.A,若将关系代数表达式:ЛR.A, R.B 2020-05-24 …
A.πA,B,C (σB=B(R×S))B.πR.A,R.B,R.C (σR.B=S.B (R×S) 2020-05-26 …
给定关系R(A,B,C,D)和关系S(C,D,E),对其进行自然连接运算R??s后的属性列为()个; 2020-05-26 …
(20)A.R.B = S.B AND R.C = S.C AND R.C < S.BB.R.B = 2020-05-26 …
若a、b、s、r都是正数,则式子:a-b/r=b/s可变行为?A.a=rb+s/sB.b=as/r+ 2020-11-03 …