问题 单项选择题

下列关于SQL语言中的索引(Index)的叙述中,哪一条是不正确的?

A.索引是外模式

B.一个基本表上可以创建多个索引

C.索引可以加快查询的执行速度

D.系统在存取数据时会自动选择合适的索引作为存取路径

答案

参考答案:A

解析:创建索引是加快表的查询速度的有效手段。可以根据需要在基本表上建立一个或多个索引, 从而提高系统的查询效率。系统在存取数据时会自动选择合适的索引作为存取路径,用户不 必也不能选择索引。

单项选择题 A1型题
阅读理解

When families gather for Christmas dinner, some will stick to formal traditions dating back to grandma’s generation. Their tables will be set with the good dishes and silver, and the dress code will be Sunday best.

But in many other homes, this china-and-silver elegance has given way to a stoneware (粗陶) and stainless informality, with dresses assuming an equally casual-Friday look. For hosts and guests, the change means greater simplicity and comfort. For makers of fine china in Britain, it spells economic hard times.

Last week Royal Doulton, the largest employer in Stoke-on-Trent, announced that it is eliminating 1,000 jobs-one-fifth of its total workforce. That brings to more than 4,000 the number of positions lost in 18 months in the pottery (陶瓷) region. Wedgwood and other pottery factories made cuts earlier.

Although a strong pound and weak markets in Asia play a role in the downsizing, the layoffs in Stoke have their roots in earthshaking social shifts. A spokesman for Royal Doulton admitted that the company “has been somewhat slow in catching up with the trend” toward casual dining. Families eat together less often, he explained, and more people eat alone, either because they are single or they eat in front of television.

Even dinner parties, if they happen at all, have gone casual. In a time of long work hours and demanding family schedules, busy hosts insist, rightly, that it’s better to share a takeout pizza on paper plates in the family room than to wait for the perfect moment or a “real” dinner party. Too often, the perfect moment never comes. Iron a fine-patterned tablecloth? Forget it. Polish the silver? Who has time?

Yet the loss of formality has its down side. The fine points of etiquette (礼节) that children might once have learned at the table by observation or instruction from parents and grandparents (“Chew with your mouth closed.” “Keep your elbows off the table.”) must be picked up elsewhere. Some companies now offer etiquette seminars for employees who may be able professionally but inexperienced socially.

67.Why do people tend to follow the trend to casual dining?

A. Family members need more time to relax.

B. Busy schedules leave people no time for formality.

C. People prefer to live a comfortable life.

D. Young people won’t follow the etiquette of the older generation

68.It can be learned from the passage that Royal Doulton is ________.

A. a seller of stainless steel tableware                      B. a dealer in stoneware

C. a pottery chain store                                                 D. a producer of fine china

69.The main cause of the layoffs in the pottery industry is ________.

A. the increased value of the pound                          

B. the worsening economy in Asia

C. the change in people’s way of life

D. the fierce competition at home and abroad

70.Formal table manners, though less popular than before in current social life, ________.

A. are still a must on certain occasions                     B. are certain to return sooner or later

C. are still being taught by parents at home                    D. can help improve personal relationships