问题 单项选择题

在分布式数据库系统中,一般不适合作为衡量查询代价依据的是______。

A.CPU代价

B.I/O代价

C.通信代价

D.存储代价

答案

参考答案:D

解析: 在集中式数据库系统中,查询代价主要是由CPU代价和I/O代价来衡量的,在分布式数据库系统中,由于数据分布在多个不同的场地上,使得查询处理中还要考虑站点间传输数据的通信代价。另外,分布式数据库的缺点之一就是复杂的存取结构。因此本题答案为D。

完形填空
In a small village, there lived a potter(陶工) who had a donkey. Every day his donkey would carry soil from the ______ to his house. Since the field was quite far off, the potter would ______ under a tree midway, tying(拴) his donkey nearby.
One day, the potter ____ to take the rope with which he tied the donkey every day. When he reached the ____, he became worried and didn’t know what to do.   At that time, a saint(圣人) ____ to be passing by. When the potter told the saint what his ____ was, he said, “Take the ____ to the place where you tie him every day. ____ to tie him using an imaginary rope. He won’t run away.” The potter did what the saint had said.
When he woke up, to his ___ and relief, he found the donkey standing in the ____ place. But to his frustration, when he prepared to leave for ____, the donkey did not move. ____, the potter saw the wise saint again and told him about the donkey’s ____ behavior. The saint said, “Go and pretend to untie the rope.” The potter ____ the saint’s advice.
Now the donkey was ready to leave for home. The potter thanked the wise saint and went home ____ his donkey.
小题1:
A.factoryB.gardenC.fieldD.village
小题2:
A.standB.restC.singD.dance
小题3:
A.forgotB.decidedC.expectedD.agreed
小题4:
A.stoneB.treeC.bridgeD.house
小题5:
A.failedB.attemptedC.happenedD.managed
小题6:
A.animalB.plantC.problemD.result
小题7:
A.birdB.flowerC.donkeyD.rope
小题8:
A.BelieveB.LearnC.WishD.Pretend
小题9:
A.surpriseB.disappointmentC.angerD.regret
小题10:
A.similarB.specialC.sameD.wrong
小题11:
A.fieldB.schoolC.homeD.hospital
小题12:
A.QuicklyB.LuckilyC.UnfortunatelyD.Badly
小题13:
A.funnyB.foolishC.properD.strange
小题14:
A.offeredB.followedC.refusedD.received
小题15:
A.happilyB.sadlyC.seriouslyD.casually
单项选择题