问题 单项选择题

数据库系统运行的基本工作单位是事务。事务通常以BEGIN TRANASCTION语句开始,以COMMIT或R<OI上BACK语句结束。COMMIT表示 (60) ,ROLLBACK表示 (61) 。在多个事务并发执行时,系统应保证与这些事务先后单独执行时的结果一样,此时事务达到了 (62) 要求。

在关系SC(emp_id,emp_name,emp_phone,dept_name,dept_phone,dept_mgmame)中,有函数依赖:(1)emp_id→emp_name,emp_phone,dept_name:(2)dept_name→ dept_phone,dept_mgmame

那么该关系满足最大范式是 (63) 。它的主要问题是数据冗余。如把SC分解成两个关系模式R1 (64) 和R2 (65) ,则可以完全解决这一问题。

64()

A.(emp_id,emp_name)

B.(emp_id,emp_name,emp_phone,dept_name)

C.(emp_name,emp_phone,dept_name)

D.(emp_id,emp_name,emp_phone,dept_name,dept_phone)

答案

参考答案:B

阅读理解

阅读理解。

     Mr. Zhang was a sports fan. He worked in a hospital in the capital. He was busy all the time and had little

time to have a rest. And one day he felt unwell and couldn't go on working. He decided to spend a week's

holiday in a quiet village where he could go swimming or fishing. He got off at a small railway station and

soon got to a quiet village. He took a room hotel and went to sleep as soon as he had a good meal.

     At first Mr. Zhang enjoyed himself there. He could do everything he wanted and went wherever he liked.

Nobody disturbed him and knocked at the door at midnight. But on the fourth day he was in trouble. After

lunch it was very hot. He went swimming in the river. Suddenly he saw a beautiful bird in a big tree. He

wanted to catch it, so he walked to it, but it found him and flew away as soon as gone. He began to pick

some flowers in the forest and before long he lost his way.

     The sun had gone down and night had fallen before Mr. Zhang found a small restaurant in another village.

He came in and told them to bring him some bread, two eggs and a glass of tea. After a while his food was

brought. Soon he ate up all the bread and eggs. When he was going to have the tea, he found there was a fly

in the glass.

     "What's in my tea?" Mr. Zhang called out, " A fly." 

     "It's impossible, sir." said the owner of the restaurant, "I had told them to pick all the flies out of your tea

before they brought it to you!"

1. From the story we can guess Mr. Zhang may be a _____.

A. engineer

B. doctor

C. tour guide

D. translator

2. Mr. Zhang decided to take this holiday because _____.

A. he was too tired to go on working

B. he was very busy all the time

C. he was paid a lot of money

D. he liked swimming and fishing

3. Mr. Zhang hoped to spend a week's holiday by _____.

A. catching birds

B. swimming or fishing

C. picking flowers

D. having good meals every day

4. Mr. Zhang went to the village from home _____.

A. by bus

B. by car

C. on foot 

D. by train

5. Mr. Zhang didn't enjoy himself in the village, did he?

A. No, he wasn't.

B. Yes, he was.

C. No, he didn't.

D. Yes, he did.

填空题