题目内容

There are two styles in the evolution of instruction set, that is CISC and RISC.Which chip

A. SOAR
B. VAX-11/780
CDC6600
D. IBM RTPC

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According to the principle of CRC calculation, given a frame-bit series M=11100111 and the

A. 111101
B. 00011
C. 11010011
D. 1101001

The main goals of Network are sharing computer resources .The resources include hardware,

A. gateway
B. router
C. software
D. server

设E、E1、E2和E3是关系数表达式,下面列出的式子中,不满足等价变换规则的是

A. πA(σπB='010'(E))=σB='010'(πA(E))
B. (E1×E2)×E3=E1×(E2×E3)
C. σA=6(σB='010'(E))=σA=6,B='010'(E)
D. σA=6(E1×E2)=(σA=6(E1))×(σA=6(E2))

设有关系R=(A,B,C),和关系代数表达式:
Ⅰ.πA,C(σB=5(R))
Ⅱ.σB=5(πA,C(R))
Ⅲ.σπA,C(πB=5(R))
上述关系代数表达式中,与SQL语句selectdistinct A,C from R where B=5等价的是

A. 都等价
B. Ⅲ
C. Ⅱ
D. Ⅰ

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