vides a(126)for information exchange among those devices. The scope of the LAN is small typically a single building or a cluster(叢)of buildings. The LAN is usually owned by the same organization that owns the(127)devices. The internal data rate of LAN is at least several Mb/s.The basic of LAN communication is broadcasting. At each station, there is a transmitter/receiver that communicates over a(128)shared, By other stations. A transmission from any one station is(129)to and received by all other stations.

A．broadcast

B．cable

C．control

D．interconnects

E．internet

A．look

B．looks

C．a(chǎn)ccount

D．a(chǎn)ccounts

esponse-oriented systems.The goal of(150)-oriented multiprocessing is to obtain high(150)(151)minimal computing cost. The techniques employed by multiprocessor operating systems to achieve this goal take advantage of an inherent processing versus input/output balance in the workload to produce(152)and(153). loading of system(154)

A．though

B．through

C．throughout

D．throughput

關(guān)系數(shù)據(jù)庫中有三種基本操作，從表中選出滿足某種條件的元素的操作稱為( )。

A．選擇

B．投影

C．連接

D．掃描

由計(jì)算機(jī)、操作系統(tǒng)、DBMS、數(shù)據(jù)庫、應(yīng)用程序及用戶等組成的一個(gè)整體叫( )。

A．?dāng)?shù)據(jù)庫系統(tǒng)

B．?dāng)?shù)據(jù)庫管理系統(tǒng)

C．文件系統(tǒng)

D．軟件系統(tǒng)

數(shù)據(jù)管理技術(shù)經(jīng)歷的人工管理階段的特點(diǎn)是( )。

A．?dāng)?shù)據(jù)和程序是相互獨(dú)立的

B．?dāng)?shù)據(jù)和程序緊密地結(jié)合

C．由程序產(chǎn)生數(shù)據(jù)

D．程序員編制程序時(shí)可以不考慮數(shù)據(jù)的存儲(chǔ)結(jié)構(gòu)

數(shù)據(jù)管理技術(shù)經(jīng)歷的數(shù)據(jù)庫管理階段的特點(diǎn)是( )。

A．?dāng)?shù)據(jù)和程序緊密地結(jié)合

B．由程序產(chǎn)生數(shù)據(jù)

C．程序和數(shù)據(jù)一一對(duì)應(yīng)

D．實(shí)現(xiàn)了數(shù)據(jù)共享、數(shù)據(jù)獨(dú)立性及完整性等

設(shè)關(guān)系模式R(A，B，C，D)，F(xiàn)是R上成立的FD集，F(xiàn)={AB→C，D→B}，ρ={ACD，BD}是R上的一個(gè)分解，那么分解ρ______。

A．保持函數(shù)依賴集F

B．丟失了AB→C

C．丟失了D→B

D．是否保持FD，由R的當(dāng)前關(guān)系確定

在關(guān)系模式R分解成數(shù)據(jù)庫模式ρ時(shí)，談?wù)摕o損連接的先決條件是______。

A．?dāng)?shù)據(jù)庫模式ρ中的關(guān)系模式之間有公共屬性

B．保持FD集

C．關(guān)系模式R中不存在局部依賴和傳遞依賴

D．存在泛關(guān)系

關(guān)系代數(shù)表達(dá)式R*S÷T-U的運(yùn)算結(jié)果是______。

可選擇的答案：