问题 单项选择题

在下面的两个关系中,职工号和部门号分别为职工关系和部门关系的主键(或称主码)。
职工(职工号,职工名,部门号,职务,工资)
部门(部门号,部门名,部门人数,工资总额)
在这两个关系的属性中,只有一个属性是外键(或称外来键、外码、外来码)。它是______。

A.职工关系的“职工号”

B.职工关系的“部门号”

C.部门关系的“部门号”

D.部门关系的“部门名

答案

参考答案:B

解析: 外关键字(或外码)的定义是:如果一个关系中的属性或属性组合并非该关系的码,但却是另外一个关系的主码,则称其为该关系的外码。而职工关系的“部门号”并非职工关系的主码,但却是部门关系的主码,所以它是职工关系的外码。

多项选择题
阅读理解

阅读理解。

     It is common and usual to see people freak out when they face challenges in their life. We all

pass in different life problems and challenges. No one is free of life problems. Only a dead man

faces no problem. As long as you are alive, challenges are everywhere.

     How do you face problems and challenges in your life? Problems and challenges are the building

blocks of your personality. They make you who you are. Besides, whether what happened in your

life builds or destructs you depends on how you look at it. If you take your problems as troubles,

they will be troubles and may cause destruction. If you take them as constructive tools, you are going

to be built up on them.

     Problems are everywhere. No one can avoid them. And they are good too. They open up a

different look and opportunity if you are willing to see. When you face troubles, do not frustrate or

freak out. Just cool yourself to think in a different direction. Think in a positive way. Every problem

has its own good as well as bad sides. Focus on the good one. Look at the bright side.

     Besides, there is always a good person, perhaps your mom or dad, or one of your friends, right

beside you who can turn everything into your best if you are willing to turn to them. No matter what

happens, they will be there to help you. Trust them and they will never let you down. All you need

to know is that you are loved wherever you are.

1. What's the meaning of the underlined phrase "freak out" in Paragraph 1?

A. Feel shy.    

B. Stay calm.  

C. Keep up.    

D. Feel upset.

2. In Paragraph 2, the writer implies that ______.

A. problems cause troubles  

B. attitude is everything

C. challenges can be avoided  

D. personalities are built on failures

3. According to the last paragraph, when we're in trouble, we ______.

A. can only depend on our parents      

B. are not alone

C. should only believe ourselves        

D. are not confident

4. What's the writer's purpose to write the passage?

A. To encourage.  

B. To compare.  

C. To prove.

D. To explain