问题 问答题

考生文件夹下有一个数据库文件“samp2.accdb”,其中存在已经设计好的2个表对象“tEmployee”和“tGroup”。请按以下要求完成设计。

建立“tGroup”和“tEmployee”两表之间的一对多关系,并实施参照完整性。

答案

参考答案:

步骤1:单击“数据库工具”选项卡下“关系”组中的“关系”按钮,然后单击“显示表”按钮,分别添加表“tGroup”和“tEmployee”,如图所示。关闭“显示表”对话框。

步骤2:选中表“tGroup”中的“部门编号”字段,拖动到表“tEmployee”的“所属部门”字段,放开鼠标,单击“实施参照完整性”复选框,然后单击“创建”按钮,如图所示。单击快速访问工具栏中的“保存,,按钮,关闭关系界面。

选择题
填空题

“This is a really exciting time — a new era is starting,” says Peter Bazalgette, the chief creative officer of Endemol. He is referring to the upsurge of interest in mobile television, a nascent industry at the intersection of telecoms and media which offers new opportunities to device-makers, content producers and mobile-network operators. And he is far from alone in his enthusiasm.

Already, many mobile operators offer a selection of television channels or individual shows, which are “streamed” across their third-generation (3G) networks. 41. ______.

Meanwhile, Apple Computer, which launched a video-capable version of its iPod portable music-player in October, is striking deals with television networks to expand the range of shows that can be purchased for viewing on the device, including “Lost”, “Desperate Housewives” and “Law & Order”.

42. ______. For a start, nobody really knows if consumers will pay for it, though surveys suggest they like the idea. Informa, a consultancy, says there will be 125m mobile-TV users by 2010. But many other mobile technologies inspired high hopes and then failed to live up to expectations. And even if people do want TV on the move, there is further uncertainty in two areas: technology and business models.

At the moment, mobile TV is mostly streamed over 3G networks. But sending an individual data stream to each viewer is inefficient and will be unsustainable in the long run if mobile TV takes off. 43. ______.

44. ______. That suggests that some shows (such as drama) better suit the download model, while others (such as live news, sports or reality shows) are better suited to real-time transmission. The two approaches will probably co-exist.

Just as there are several competing mobile-TV technologies, there are also many possible business models. Mobile operators might choose to build their own mobile-TV broadcast networks; or they could form a consortium and build a shared network; or existing broadcasters could build such networks.

The big question is whether the broadcasters and mobile operators can agree how to divide the spoils, assuming there are any. Broadcasters own the content, but mobile operators generally control the handsets, and they do not always see eye to eye. 45.

Then there is the question of who will fund the production of mobile-TV content: broadcasters, operators or advertisers Again, the answer is probably “all of the above”.

A.So the general consensus is that 3G streaming is a prelude to the construction of dedicated mobile-TV broadcast networks, which transmit digital TV signals on entirely different frequencies to those used for voice and data. There are three main standards: DVB-H, favoured in Europe; DMB, which has been adopted in South Korea and Japan; and MediaFLO, which is being rolled out in America. Watching TV using any of these technologies requires a TV-capable handset, of course.

B.In contrast, watching downloaded TV programmes on an iPod or other portable video player is already possible today. And unlike a programme streamed over 3G or broadcast via a dedicated mobile-TV network, shows stored on an iPod can be watched on. an underground train or in regions with patchy network coverage.

C.In South Korea, television is also sent to mobile phones via satellite and terrestrial broadcast networks, which is far more efficient than sending video across mobile networks. In Europe, the Italian arm of 3, a mobile operator, recently acquired Channel 7, a television channel, with a view to launching mobile-TV broadcasts in Italy in the second half of 2006.

D.Despite all this activity, however, the prospects for mobile TV are unclear.

E.Assuming the technology and the business models can be sorted out, there is still the tricky matter of content.

F.In South Korea, a consortium of broadcasters launched a free-to-air DMB network last month, but the country’s mobile operators were reluctant to provide their users with handsets able to receive the broadcasts, since they were unwilling to undermine the prospects for their own subscription-based mobile-TV services.

G.The potential for mobile TV is vast, in short — but so is the degree of uncertainty over how it should actually be put into practice.

43().