问题 单项选择题

在数据库系统中,用户所见的数据模式为【 】

A.概念模式

B.外模式

C.内模式

D.物理模式

答案

参考答案:B

解析:数据库管理系统的三级模式结构由外模式、模式和内模式组成。外模式也称子模式或用户模式,是指数据库用户所看到的数据结构,是用户看到的数据视图。模式也称逻辑模式,是数据库中对全体数据的逻辑结构和特性的描述,是所有用户所见到的数据视图的总和。内模式也称存储模式或物理模式,是指数据在数据库系统内的存储介质上的表示,即对数据的物理结构和存取方法的描述。根据上述介绍可知,数据库系统中用户所见到的数据模式为外模式。因此,本题的正确答案是B。

阅读理解

Bexley Middle School eighth-graders won the grand prize at the 2009 National Engineers Week Future City Competition (TM) on Feb. 18 in Washington, D.C. They competed with 37 other schools across the country.

The students qualified for the national competition by winning a regional competition on Jan. 17 in Columbus. By winning the national event, the students earned an all-expenses paid trip to Space Camp in Huntsville, Ala., according to a Bexley school district news report.

Future City aims to stir (激发) interest in science, technology, engineering and math among young people. Bexley team members were Tom Krajnak, Abby Sharp, Wyatt Peery, Elizabeth Maher, Aaron Hutchinson and Truman Haycock. They work in teams under the guidance of a teacher, Margaret Englehardt, and a volunteer engineer, Mark Sherman, design and build a city of tomorrow. Mayor John Brennan presented the students during a recent Bexley City Council meeting. Each team in the Future City competition plans its city using Sim City software and creates a model to show a physical representation of one section of the city. Team members must write both an essay about the yearly theme and an abstract about their city. They also must make a presentation to judges.

Focusing on eco-responsibility, the Bexley team built “Novo-Mondum,” an Icelandic city in the year 2171. Krajnak said the team’s project included a new water system for each resident unit and a 500-word essay on using bacteria to purify water. “We used our essay and abstract (摘要) to build a model,” he said. “It was hard to organize which building would go where, what each building does and how to make it look good.”

Englehardt said her students did a good job answering impromptu (即席) questions during the regional competition. “They can think on their feet,” she said. Principal Harley Williams said the school is very proud of the students’ performance.

小题1:.. From the passage we can learn that the grand prize winners will _________.

A.receive scholarship for further studies

B.get a free trip to Space Camp in Huntsville

C.earn a large sum of money for their designs

D.be admitted to universities without exams小题2:.The goal of the Future City competition is to _________.

A.make the Sim City software popular

B.test the students’ knowledge of city planning

C.select future engineers from young students

D.make students become interested in engineering小题3:. Each team must do the following EXCEPT _________.

A.write brief abstracts describing their city

B.present and defend their designs before judges

C.build a future city in Iceland by themselves

D.create model cities using the Sim City software小题4:. According to Margaret Englehardt, the students _________.

A.always stand still in the competition

B.react very quickly to the questions

C.prepare for the questions in advance

D.take pride in the advisers’ performance小题5:

问答题 简答题