Dry

1. The following account of the basic concepts of the database, which one is wrong?
A) "database" is understood to be stored in a computer data storage device according to a certain format Warehouse
B) is a database within the computer and may, consistent logically organized according to a certain structure of long-term storage, a large number of related shareable associated data set
C) data in the database generally have a larger redundancy
D) data in the database is organized according to a certain data models together

Answer: C

Data redundancy: means unnecessary repeated data stored in the memory.

2. There are various types of database users, they have the skills and knowledge levels vary, the purpose of a database are not the same. Accordingly, in order to facilitate their use, the DBMS should provide various types of
A) a data structure
B) Relationship Model
C) object structure
D) a user interface

Answer: D

PS: to provide users should be able to understand the user, it is clear that only the user interface

3. The following account of the data model, which one is wrong?
A) data model is used to describe the organization of data and the real world processing tool
B) is mainly used for static characteristic data model definition of a database, but not easy to describe the dynamic behavior between the data
C) requires the data model can simulate more realistic real-world
D) data model is the core and foundation of database systems

Answer: B

Database model describes the structure moiety and methods for manipulating data in the database model specifies how data is described (e.g., tree, table, etc.). Manipulation part of the model specifies the data to add, delete, display, maintain, print, search, select, sort, and update operations.

Database model , including conceptual model, hierarchical model, network model, relational model, object-oriented model

Database model is not a data model

4. If a course can only be taught by a teacher, and a teacher can teach a number of courses, the links between the curriculum and the teachers of these two entities is type
A) one
B) many-
C) many
D) many to one

Answer: D

5. The following account of the concept model, which one is wrong?
A) is a conceptual model of the real world to the world of abstract information
B) is a conceptual model from the point of view of the user data and modeling information
) conceptual model with a strong grammar skills C, but can not describe the semantic information
D) entity - relationship model It is the most common conceptual model

Answer: C

Conceptual Model ---> --- logical model> physical model

(The specific details of the process gradually)

Conceptual model is independent of the model of a computer system, that did not involve the internal representation of the computer, nor on the particular computer system. Semantic abstraction from the real world to the world of information for the conceptual design of a database

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6. The following account of the database "type" and "value" Which one is wrong?
A) in the database refers to a type of class data structures and properties described
type B) occur over time the database is changing
C) database also referred connotation database
D) is the value of the database-type a specific assignment

Answer: B

The concept of "type" and "value" in the data model. Type is a structure and properties of a class of data, a specific value is assigned type. For example, student records is defined as (student number, name, sex, department, age, place of origin) such a record type, and (201,315,130, Li Ming, male, Department of Computer Science, 19, Nanjing, Jiangsu) is the type of record a record value. - From "Introduction to Database Systems" on page 27 under the fifth edition

Ps: to as "type" is equal to a data structure, "value" is an example of the data structure

7. The following statements about the relational data model, which one is wrong?
Physical Configuration A), the relational model is a two-dimensional data table
B) in the relational model, the linkages between the real-world entities and entities are represented by the relationship
C) to insert, delete, update of the relational model is the common operation
D) through the relationship language relational operations, the relationship between the characteristics of the language is highly non-procedural

Answer: A

Relational data model is a collection of a number of relational schema thereof. Examples of relational schema called a relationship. Each relationship can see a two-dimensional table, each row of the table is called a tuple that identifies a centralized entity entity; column called attribute table, the column name is the attribute name, attribute name is not the same

A: From a user perspective, the relational model of data in the logical structure is a two-dimensional table

It is the actual physical structure of storage structure

8. The following account of the relationship between the data of the language, which one is wrong?
A) is a relational algebra traditional relational operators language representation, is an abstract query language
B) tuple relational calculus and the relational calculus belonging domain relational calculus language
C) having a relational algebra more expressive than relational calculus
D ) SQL language is an important language of relational data

Answer: C

Relational algebra is an abstract query language ( procedural query language ) , with operations on relationship to express queries, study mathematical tools as relational language. Relational algebra operands are relations operation is also a result of the relationship. Used in relational algebra operators include four categories: set operators, relational operators specialized arithmetic comparison operators, and logical comparison operators, and logical operators are used to assist operators specialized operating relation, so in accordance with the different operators, mainly into relational algebra traditional set operations and specialized arithmetic relationship types. ( Union, intersection, difference, generalized Cartesian product | selection, projection, is connected, in addition )

Tuple relational calculus ( tuple Relational Calculus ) is a non-procedural of (nonprocedural) Query Language, describes only the required information, without giving a specific process to obtain this information.

Domain relational calculus ( Domain Relational Calculus ): Another form of relational calculus, field variables using values from the attribute domain, rather than the value of the entire tuple.

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  Relational algebra Portal

Eg:

R

A B C

a1 b1 c1

a1 b2 c2

a2 b2 c1


S

A B C

a1 b2 c2

a1
b3
c2

a2 b2 c1

Generalized Cartesian product

(R and S of the first row of the three rows are matched, the second row of three rows R and S respectively match .....)

R
A	B	C
a1	b1	c1
a1	b2	c2
a2	b2	c1

S
A	B	C
a1	b2	c2
a1	b3	c2
a2	b2	c1

9. The three existing relationship "Student - - Optional Course" database is as follows:
S (S #, SNAME, SEX, Birthyear, the DEPT), a master key S #

C (C #, CNAME, TEACHER), the master key is C #

SC（S#，C#，GRADE），主码是（S#，C#）
下列关于保持数据库完整性的叙述中，哪一条是错误的？
A) 向关系SC插入元组时，S# 和C# 都不能是空值（NULL）
B) 可以任意删除关系SC中的元组
C) 向任何一个关系插入元组时，必须保证关系主码值的唯一性
D) 可以任意删除关系C中的元组

答案：D

10.在关系代数中，从两个关系的笛卡尔积中选取它们属性间满足一定条件的元组的操作称为
A) 并
B) 选择
C) 自然连接
D) 连接

答案：D

11. 下列关于关系代数基本运算的等式中，哪一个是正确的？
A) R - (R - S) = S
B) R - (R - S) = RS
C) R - (S - R) = S
D) R - (S - R) = R S

答案：B

12.SQL语言十分简洁，完成数据定义、数据操纵、数据控制的核心功能只用了9个动词。下列动词中哪一个是用于数据定义的？
A) ALTER
B) DELETE
C) GRANT
D) INSERT

答案：A

13.下列关于SQL语言支持数据库三级模式结构的叙述中,哪一条是错误的
A) 一个SQL数据库模式是该数据库中基本表的集合
B) 在SQL中，外模式对应于"视图(view)"和部分基本表
C) 基本表和索引都存放在存储文件中
D) 一个基本表只能存放在一个存储文件中

答案：D

14.下列关于关系数据库视图的叙述中，哪一条是错误的？
A) 视图是关系数据库系统提供给用户以多种角度观察数据库中数据的重要机制
B) 视图可对重构数据库提供一定程度的逻辑独立性
C) 所有的视图都是可查询和可更新的
D) 对视图的一切操作最终要转换为对基本表的操作

答案：C

15.下列关于将SQL嵌入主语言使用的叙述中，哪一条是错误的
A) 必须协调SQL语句与主语言语句处理记录的不同方式
B) 必须处理数据库工作单元和程序工作单元之间的通信
C) 与游标相关的有4个语句：游标定义、游标打开、游标推进、游标关闭
D) 游标一旦关闭，就不能再重新打开

答案：D

16.基于"学生-选课-课程"数据库中的三个关系：
S（S#，SNAME，SEX，BIRTHYEAR，DEPT），主码为S#
C（C#，CNAME，TEACHER），主码为C#
SC（S#，C#，GRADE），主码为（S#，C#）
为了提高查询速度，对SC表创建唯一索引，应该建立在哪个（组）属性上？
A) S#
B) C#
C) GRADE
D) (S#, C#)

答案：D

17.基于"学生-选课-课程"数据库中的三个关系：
S（S#，SNAME，SEX，BIRTHYEAR，DEPT），主码为S#
C（C#，CNAME，TEACHER），主码为C#
SC（S#，C#，GRADE），主码为（S#，C#）
查找"选修了至少5门课程的学生的学号"，正确的SQL语句是
A) SELECT S# FROM SC GROUP BY S# HAVING COUNT（*）≥ 5
B) SELECT S# FROM SC GROUP BY S# WHERE COUNT（*）≥ 5
C) SELECT S# FROM SC HAVING COUNT（*）≥ 5
D) SELECT S# FROM SC WHERE COUNT（*）≥ 5

答案：A

18.基于"学生-选课-课程"数据库中的三个关系：
S（S#，SNAME，SEX，BIRTHYEAR，DEPT），主码为S#
C（C#，CNAME，TEACHER），主码为C#
SC（S#，C#，GRADE），主码为（S#，C#）
查找"选修了C01号课程的全体学生的姓名和所在的系"，下列SQL语句中哪一个是错误的？
A) SELECT SNAME, DEPT FROM S WHERE S# IN (SELECT S# FROM SC WHERE C# ='C01')；
B) SELECT SNAME, DEPT FROM S WHERE S# = (SELECT S# FROM SC WHERE C# ='C01')；
C) SELECT SNAME, DEPT FROM S, SC WHERE C# ='C01' AND S.S# = SC.S#；
D) SELECT SNAME, DEPT FROM (S JOIN SC ON S.S# = SC.S#) WHERE C# ='C01'；