问题 填空题

在并发控制中,事务是数据库的逻辑工作单位,是用户定义的一组操作序列。一个程序可以包含多个事务,事务是并发控制的【 】。

答案

参考答案:单位

解析:事务是数据库的逻辑工作单位,是用户定义的一组操作序列。如在关系数据库中,一个事务可以是一组SQL语句、一条SQL语句或整个程序。通常情况下,一个应用程序包括多个事务。DBMS的并发控制是以事务为单位进行的。

阅读理解

阅读理解。

     By Zhang Youlv (China Daily 09/29/2008)-A manned lunar (月球的) landing is China's next target when the

current three-stage space program ends in the next dacade."When our manned space program is completed,

we will travel even further," Wang Zhaoyao, deputy head of China's manned space program office and

Shenzhou VII mission spokesman, told a briefing in Beijing three hours after China's third manned space

mission was successfully concluded yesterday.

     "After comprehensively analyzing the general trend of the international development of manned space, as

well as realities in China, we see a manned lunar landing as a both challenging and tactical (策略的) field in

global hi-tech," he said.

     "We believe it necessary for our country to do something in this field," Wang said.

     He did not give a specific(具体的) date for a moon landing. Wang, however, said,"Experts believe this is

'very much needed' for research into relevant (closely connected) technologies to further China's achievements

in space."

      The 68-hour Shenzhou VII mission featured a 25-minute spacewalk on Saturday.

      It was broadcast live and watched by millions throughout the country. The crew's landing at a site in the

Inner Mongolia autonomous region was also carried live by national television.

     The entire mission was pronounced a complete success.

     Wang said the three astronauts, were transported to Hohhot, the region's capital, and would spend the

evening there.

     "They will return to Beijing this morning," he said.

     "During the course of the mission, Russian experts provided strong technical support for the EVA

spacesuits. The successful Sino-Russian cooperation for this flight created beneficial conditions for more

intensive cooperation between the two sides in the future," Wang said.

     The mission's success has paved the way for completing the second stage of the program-building a space

station before 2020.

      Before that, a space lab will be set up in 2010 with Shenzhou X, the country's next full-crew space journey.

1. When will China's spaceship land on the moon?

A. 2020.

B. 2010.

C. 2018.

D. No specific date.

2. What does the underlined sentence in the fourth paragraph imply?

A. We will travel even further in the outer space.

B. There is a need for China to land on the moon.

C. It is very much needed to research space technologies to further China's space program.

D. International cooperation is necessary for China's landing on the moon.

3. The reason why Russian experts provided strong technical support for the EVA spacesuits is that _____.

A. China can't make spacesuit

B. China and Russia would like to cooperate in space program

C. China is a leading technological power now

D. Russia wants to benefit from China

4. What would be the best title for this passage?

A. A Manned Lunar Landing is Both Challenging and Tactical

B. Shenzhou X will Land on the Moon

C. China will Set up a Space Lab on the Moon

D. Landing on the Moon--the Next Target

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