题目内容

数据模型定义了数据库系统中数据组织、存储和管理必须遵循的规范,可以分为概念数据模型、数据结构模型和物理数据模型三大类。其中概念数据模型的典型代表是

A. 实体-联系模型
B. 关系模型
C. 面向对象模型
D. 网状模型

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需求包括许多方面的内容。其中,描述系统中数据定义以及数据间的联系属于下列哪方面的内容

A. 约束
B. 数据需求
C. 转换
D. 功能

在下列各种编码中,每个字节最高位均是“1”的是( )。

A. 汉字国标码
B. 汉字机内码
C. 外码
D. ASCII码

During recent years we have heard much about "race": how this race does certain things and that race believes certain things and so on. Yet, the (21) phenomenon of race consists of a few surface indications.We judge race usually (22) the coloring of the skin: a white race, a brown race, a yellow race and a black race. But (23) you were to remove the skin you could not (24) anything about the race to which the individual belonged. There is (25) in physical structure, the brain or the internal organs to (26) a difference.There are four types of blood. (27) types are found in every race, and no type is distinct to any race. Human brains are the (28) . No scientists could examine a brain and tell you the race to which the individual belonged. Brains will (29) in size, but this occurs within every race. (30) does size have anything to do with intelligence. The largest brain (31) examined belonged to a person of weak (32) .On the other hand, some of our most distinguished people have had (33) brains.Mental tests which are reasonably (34) show no differences in intelligence between races. High and low test results both can be recorded by different members of any race. (35) equal educational advantages, there will be no difference in average standings, either on account of race or geographical location. Individuals of every race (36) civilization to go backward or forward. Training and education can change the response of a group of people, (37) enable them to behave in a (38) way.The behavior and ideals of people change according to circumstances, but they can always go back or go on to something new (39) is better and higher than anything (40) the past. 38().

A. same
B. identical
C. similar
D. alike

关系模式Student(Sno,Sname,Cno,Cname,Grade,Tname,Taddr)的属性分别表示学号、学生姓名、课程号、课程名、成绩、任课教师名、教师地址。其中,一个学生可以选若干门课程,一个教师可以讲授若干门课程,一门课程可以由多个教师讲授,对于同一门课程,学生只能选定一个教师讲授的课程,教师不会重名。下列有关关系模式Student的分解中,是无损连接并保持函数依赖的是

A. (Sno,Sname,Cno,Tname,Taddr),(Sno,Sname,Cno,Cname,Grade)为1NF
B. (Sno,Sname),(Sno,Cno,Grade,Tname,Taddr),(Cno,Cname)为2NF
C. (Sno,Sname),(Sno,Cno,Grade),(Tname,Taddr),(Cno,Cname))为3NF
D. (Sno,Sname),(Sno,Cno,Grade),(Tname,Taddr),(Tname,Cno),(Cno,Cname)为BCNF、

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