关系代数运算是以集合操作为基础的运算,其五种基本运算是并、差、__(1)__、投影和

题型:单项选择题 案例分析题

问题:

关系代数运算是以集合操作为基础的运算,其五种基本运算是并、差、__(1)__、投影和选择,其他运算可由这些运算导出。为了提高数据的操作效率和存储空间的利用率,需要对__(2)__进行分解。

空白(2)处应选择()

A.内模式

B.视图

C.外模式

D.关系模式

考点:计算机软件水平考试初级程序员初级程序员模拟试卷一(上午)
题型:单项选择题 案例分析题

阅读理解。

     Air is all around us. At the time we are born, air is around us everywhere (任何地方). We live in air.

     All living things need air. Living things cannot live without(没有) air. We can go without food or

water for a few days, but we can't live a few minutes without air. We take in air. When we are working,

we need more air. When we are sleeping, we need less air.

     We live in air but we cannot see it. We can only feel it. We can feel it when it is moving. Moving air

is called wind. How can you make air move? Here is one way. Take an open book in your hands in

front of your face. Close it quickly. What can you feel? It is air.

1.Where is air?

A. It's on the table.

B. It's all around us.

C. It's near us.

D. It's not here.

2. What do all living thing need?

A. Wind.

B. Clothes.

C. Air.

D. Food.

3. Moving air is called           .

A. wind

B. rain

C. snow

D. cloud

4. When do we need more air?

A. Sleeping.

B. Sitting.

C. Working.

D. Standing.

5. What does the word "less" in the passage mean?

A. 多于

B. 少量

C. 没有

D. 更多

题型:单项选择题 案例分析题

下列不屈于建设项目财务管理的基本职能的是()。

A.财务预算

B.财务需求

C.财务预测

D.财务报告

题型:单项选择题 案例分析题

CT质量控制中最常用的测试空间分辨率方法是 ()

A.PSF

B.LSF

C.CTF

D.MTF

E.ERF

题型:单项选择题 案例分析题

反应烧结机生产率的指标是()。

A、台时

B、利用系数

C、作业率

题型:单项选择题 案例分析题

已知A=E+αβT,其中α=(a1,a2,a3)T,β=(b1,b2,b3,)T,且αTβ=2.

求矩阵A的特征值与特征向量;

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