问题 单项选择题

假设职工EMP(职工号,姓名,性别,进单位时间,电话),职务JOB(职务,月薪)和部门DEPT(部门号,部门名称,部门电话,负责人)实体集,若一个职务可以由多个职工担任,但一个职工只能担任一个职务,并属于一个部门,部门负责人是一个职工。图中EMP和JOB之间为 (30) 联系;假设一对多联系不转换为一个独立的关系模式,那么生成的关系模式EMP中应加入 (31) 关系模式的主键,则关系模式EMP的外键为 (32)

(32)处应填()。

A.部门号和职工号

B.部门号和职务

C.职务和负责人

D.部门号和负责人

答案

参考答案:B

解析:

试题(30)~(32)

[分析]:

本题考查的是应试者对数据库系统中ER模型方面的基础知识。

根据题意,职工EMP关系中一个职工只能担任一个职务,并属于一个部门,因此职工EMP和部门DEPT关系之间是一个一对多的联系1 *,故a应为EMP关系;又因为一个职务可以由多个职工担任,所以职工EMP和职务JOB关系之间是一个多对一的联系 * 1

职务JOB(职务,月薪)关系的主码为职务,部门DEPT关系的主码为部门号,因此根据外码是另一个关系中的主码的定义;职工EMP关系中的外码为部门号和职务。

阅读理解

The bedroom door opened and a light went on, signaling an end to nap time.The toddle(初学走路的婴儿), sleepy-eyed, clambered to a swinging stand in his crib.He smiled, reached out to his father, and uttered what is fast becoming the cry of his generation: "iPhone!"

Just as adults have a hard time putting down their iPhones, so the device is now the Toy of Choice for many 1-, 2- and 3-year-olds.The phenomenon is attracting the attention and concern of some childhood development specialists.

Natasha Sykes, a mother of two in Atlanta, remembers the first time her daughter, Kelsey, now 3 but then barely 2 years old, held her husband's iPhone."She pressed the button and it lit up.I just remember her eyes.It was like 'Whoa!' "The parents were charmed by their daughter's fascination.But then, said Ms.Sykes (herself a Black Berry user), "She got serious about the phone." Kelsey would ask for it.Then she'd cry for it."It was like she'd always want the phone," Ms.Sykes said.

Apple, the iPhone's designer and manufacturer, has built its success on machines so user-friendly that even technologically blinded adults can figure out how to work them, so it makes sense that sophisticated children would follow.Tap a picture on the screen and something happens.What could be more fun?

The sleepy-eyed toddler who called for the iPhone is one of hundreds of iPhone-loving toddlers whose parents are often proud of their offspring's ability to slide fat fingers across the gadget's screen and pull up photographs of their choice.

Many iPhone apps on the market are aimed directly at preschoolers, many of them labeled "educational," such as Toddler Teasers: Shapes, which asks the child to tap a circle or square or triangle; and Pocket Zoo, which streams live video of animals at zoos around the world.

Along with fears about dropping and damage, however, many parents sharing iPhones with their young ones feel guilty.They wonder whether it is indeed an educational tool, or a passive amusement like television.The American Academy of Pediatrics is continually reassessing its guidelines to address new forms of "screen time." Dr.Gwenn Schurgin O'Keeffe, a member of the academy's council, said, "We always try to throw in the latest technology, but the cellphone industry is becoming so complex that we always come back to the table and wonder- Should we have a specific guideline for them?"

Tovah P. Klein, the director of a research center for Toddler Development worries that fixation on the iPhone screen every time a child is out with parents will limit the child's ability to experience the wider world.

As with TV in earlier generations, the world is increasingly divided into those parents who do allow iPhone use and those who don't. A recent post on UrbanBaby.com, asked if anyone had found that their child was more interested in playing with their iPhone than with real toys. The Don't mothers said on the Website: "We don't let our toddler touch our iPhones ... it takes away from creative play." "Please ... just say no. It is not too hard to distract a toddler with, say ... a book."

Kathy Hirsh-Pasek, a psychology professor who specializes in early language development, sides with the Don'ts. Research shows that children learn best through activities that help them adapt to the particular situation at hand and interacting with a screen doesn't qualify, she said.

Still, Dr. Hirsh-Pasek, struck on a recent visit to New York City by how many parents were handing over their iPhones to their little children in the subway, said she understands the impulse (冲动). "This is a magical phone," she said. "I must admit I'm addicted to this phone."

小题1:The first paragraph in the passage intends to ______.

A.get us to know a cute sleepy-eyed child in a family

B.show us how harmful the iPhone is

C.lead us to the topic of the toddlers' iPhone-addict

D.explain how iPhone appeals to toddlers小题2:According to the author, iPhones are popular with both adults and young kids because they are______.

A.easy to use

B.beautiful in appearance

C.cheap in price

D.powerful in battery volume小题3:The underlined word "them" in the seventh paragraph refers to ______.

A.televisions

B.cellphones

C.iPhones

D.screens小题4:The tone of the author towards parents sharing iPhones with their children is ______.

A.negative

B.subjective

C.objective

D.supportive小题5:The passage mainly tells us ______.

A.children's iPhone addict is becoming a concern

B.iPhone is winning the hearts of the toddlers

C.Apple is developing more user-friendly products

D.ways to avoid children's being addicted to iPhone games

单项选择题