问题 填空题

关系数据库的规范化理论规定,在执行分离时,必须遵守 【10】 ,保持原有的依赖关系和无损连接。

答案

参考答案:(10) 规范化原则

解析:解析:规范化过程中将一个关系模式分解为若干个关系模式,必须遵守规范化原则,应该保证分解后产生的模式与原来的模式等价。常用的等价标准有要求分解是具有无损连接性和要求分解是保持函数依赖的两种。

阅读理解

Volunteering means that you work to help people without being paid. There are many different volunteers. They help people who really need help. There are many places where you can be volunteers. Here are just a few places for you.

Hospital---ask if you can go and visit people who are really sick. Sometimes what they need is someone to talk to, or someone to give them hope.

Orphanage (孤儿院) ---the children living there really need someone to play with them.

Food Shelter---many food shelters need people to clean up the shelters and help give out food or water to those who need it.

Home for the elderly ---help the elderly people clean up their homes.

Community (社区) Center ---a lot of community centers are very well run. However, some of them really need extra help, especially cleaning and repairs.

As a student you can also do a lot of things to help others at school. Maybe you could start a support group.

Here is some advice:

Help students give up smoking, drinking or other bad habits.

Help students who come from poor families.

Help new students get used to their school life soon.

Provide seniors with information on future studies.

小题1: Volunteers can’t get      when they help others.

A.everything

B.money

C.some presents

D.a job小题2:How many places are mentioned for you to be volunteers in according to this passage?

A.Six

B.Five

C.Four

D.Three小题3:The volunteers can      in the community center.

A.make the sick hopeful

B.give out food or water

C.play with the children

D.clean up the center小题4:Which of the following volunteer jobs can be done at school except      .

A.helping students who come from poor families

B.helping the students who have bad habits

C.helping the student to copy others’ homework

D.helping the students in trouble with their studies

多项选择题