问题 单项选择题

在SQL语言中,一个基本表的定义一旦被删除,则与此表相关的下列内容中( )也自动被删除。 Ⅰ、在此表中的数据 Ⅱ、在此表上建立的索引 Ⅲ、在此表上建立的视图

A.Ⅰ和Ⅱ

B.Ⅱ和Ⅲ

C.Ⅰ和Ⅲ

D.全部

答案

参考答案:A

解析: 一个SQL数据库是表的汇集,一个SQL表是由行集构成,一行是列的序列,每列对应一个数据项,一个表可以带若干索引,索引也存放在存储文件中,一个表或者是一个基本表,或者是一个视图,一个基本表可以跨一个或多个存储文件存放,SQL语言支持数据库的三级模式结构。

判断题
阅读理解

阅读理解。

      American children and teenagers have increased their use of entertainment media by more than one hour

a day in the last five years. On an average day they now spend seven and a half hours using media.

     These are the findings of a new survey. It included not only devices like TVs, computers, mobile phones

and MP3 players, but also media like books and magazines. It did not count media use for school.

     Vicky Rideout at the Kaiser Family Foundation, a health re- search group, wrote the report. She was

surprised that kids could fit even more media time into their day.

     She found that they spent ten hours and fortyfive minutes if you counted each device individually. But

children multi-task a lot, and Vicky Rideout says this is not necessarily a good thing. "

     People who study the brain will tell you that you can't actually multitask in that way. You're really

switching back and forth in order from different tasks, just doing it rapidly, and that you don't really do either

task as well as you would do them if. you did them one at a time." she added.

     The study suggests a link between heavy media use and lower performance in school. About one-fourth of

those who used media the least reported that their grades were mostly average or below. But that was true of

half the heavy media users.

     So where are the parents? Children who had any rule limiting the use of any kind of media were exposed to

an average of about three hours less media a day. But only one-third of children had to follow any rules.

     Girls spent more time than boys on social networking sites, lis tening to music and reading. Boys spent

more time on video games-an average of forty eight minutes more a day than girls.

     Vicky said "It looks like the girls just sort of lose interest in the games and they drop off and start doing

other things, whereas the boys' interest remains strong."

     Some other findings: Time spent reading books has not dropped in the last five years. But time with

newspapers and magazines has, though some reading now takes place online.

1. What is worrying about American children and teenagers according to the survey?

A. The burden and pressure of study after school.

B. The money spent on the entertainment media.

C. Their increased time spent on entertainment media.

D. The lost control of their entertainment activities.

2. What does the underlined word "multitask" mean?

A. Doing different tasks without being permitted.

B. Carrying many tasks at the same time.

C. Doing some illegal things out of school.

D. Only doing one task in the limited time.

3. The underlined sentence in Paragraph 7 means____.

A. Parents should watch children while they are using media

B. Parents shouldn't allow children use media at all

C. Parents should hide and give children free space

D. Parents should play an important part as a director