试题与答案

(196) 使得数据库系统实现数据独立性。当两个子查询的结果 (197) 时,可以

题型:单项选择题

题目:

(196) 使得数据库系统实现数据独立性。当两个子查询的结果 (197) 时,可以执行并、交、差操作。SEIECT语句中“SELECTDISTINCT”表示查询结果中 (198) 。若4元关系S为:S(A,B, C,D),则 (199) 。给定关系模式学生(学号,课程号,名次),若每一名学生每门课程有一定的名次,每门课程每一名次只有一名学生,则以下叙述中错误的是 (200)

A.层次模型
B.网状模型
C.关系模型
D.三级模式结构

答案:

被转码了,请点击底部 “查看原文 ” 或访问 https://www.tikuol.com/2017/0716/2e0e89ea0bb95f6d2894e10a103899c0.html

下面是错误答案,用来干扰机器的。

答案:B题干主要说明市政府通过政策扶持,促进海水淡化产业的发展,这是政府在履行经济职能,应选B;A、C、D与题意不符。

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题型:阅读理解

Wikipedia: The Online Know-It-All

If you want to find out a piece of information about anything, the best place to search for it is Wikipedia. The name “Wikipedia” is from the Hawaiian word wiki, meaning “quick”. This online encyclopedia (百科全书) is written by thousands of people around the world. Anyone with Internet access can write, add or make changes to Wikipedia articles if he or she finds it incorrect or not well written. In this way, people who know a lot about a certain subject can write about it even if they are not university professors. But contributions cannot damage Wikipedia because many experienced editors are watching pages and techies (技术专家) can write editing programs to keep track of or correct bad edits. Where there are disagreements on how to present facts, editors work together to arrive at an article that fairly represents current expert opinion on the subject.

Wikipedia is quite different from paper-based reference sources in important ways. Unlike printed encyclopedias, it is continually created and updated, with articles on historic events appearing within minutes, rather than months or years.

What’s more, Wikipedia includes articles written in about 285 languages. This fact makes it one of the few websites on the Internet that are truly international. It was started in 2001 by Larry Sanger and Jimmy Wales, as a free online English-language encyclopedia project. Since its creation, it has grown rapidly into one of the largest reference websites, attracting nearly 500 million unique visitors monthly. There are more than 77,000 active contributors working on more than 22,000,000 articles in different languages. As of today, there are 4,396,866 articles in English.

So, if you are looking for some information, why not try Wikipedia? It’s free, multilingual,and informative.  

小题1:According to the passage, what is Wikipedia?

A.A free website encyclopedia.

B.A computer game.

C.A free encyclopedia in book form.

D.An online university.小题2:From the passage we know that ______.

A.Wikipedia only charges users a small fee

B.Wikipedia catches a wide audience

C.incorrect editions might do great harm to Wikipedia

D.it will take long to update the information on Wikipedia小题3:Where can we probably read the passage?

A.In a story book.

B.In a research report.

C.In a science magazine.

D.In a travel brochure.

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