1 List four examples of database systems other than those listed in Section 1.1.
使用公交卡，使用市民卡，使用校园一卡通购物，打卡上班
2 Discuss the meaning of each of the following terms:
(a) data
data is the physical symbols that represent different kinds of information.
(b) database
A Shared collection of logically related data (and a description of this data), designed to meet the information needs of an organization.
(c) database management system
is a software system that enables users to define, create, and maintain the database and that provides controlled access to this database.
(d) data independence
This is essentially the separation of underlying file structures from the programs that operate on them,also called program-data independence.
(f) views.
A virtual table that does not necessarily exist in the database but is generated by the DBMS from the underlying base tables whenever it’s accessed.
3 What is the difference between conceptual and logical data models? Give examples of each.
Used to describe data independently of any system；
Purpose is to represent the concepts of the real world；
Used in early stages of database design；
Example: entity-relationship (E-R) model
Used in DBMSs for the organization of data at a level that abstracts from physical structures
Example:the relational data model
4 Define the terms relation, schema, instance and attribute. Give examples.
Answer:
Relations is a table with columns and rows.
Example:Courses（course,tutor,room）
The schema represents the structure of the data .
Example:Schema of Courses is (Course, Tutor, Room)
The instance represents the actual values.
Example:The instances of Courses are the contents of the tables
An attribute is a named column of a relation
Example:the information on course is represented by the course relation,with column for attributes Course,Tutor,Room
5 What is the purpose of the three levels (i.e. physical, logical and external) for a DBMS?
separate each user’s view of the database from the way the database is physically represented.
6 What is the difference between the DML and DDL parts of SQL? What part would you use to (i) create a table to hold information about employees, (ii) add information about a new employee to the table, and (iii) find out the salary of one of the employees?
The database administrator often interacts with the database via a “Data Definition Language” or DDL.Database users interact with the database via a “Data Manipulation Language” or DMLDDL;DML
7 Describe the five components of the DBMS environment and discuss how they relate to each other.
Hardware
:The computer system(s) that the DBMS and the application programs run on. This can range from a single PC, to a single mainframe(主机), to a network of computers.
Software:
The DBMS software and the application programs, together with the operating system, in
cluding network software if the DBMS is being used over a network.
Data:
Used by the organization.
The data acts as a bridge between the hardware and software components and the human components. Procedures:
Instructions and rules（操作说明和规则） that should be applied to the design and use of the database and DBMS.People:Includes DBMS designers and implementers(实现者), database designers, database administrators ( DBAs), application programmers, and end-users.8 What is logical data independence?
Logical data independence refers to the immunity of the external schema to the changes in the conceptual schema.
9 what is physical data independence?
Physical data independence refers to the immunity of the conceptual schema to the changes in the internal schema.
10 what is data model? Describe the components of data model.
A data model is a set of constructs used to organize data.
A data model can be thought of as comprising three components:
a structural part,consisting of a set of rules according to which databases can be constructed;
a manipulative part,defining the types of operation that are allowed on the data(this includes the operations that are used for updating or retrieving data from the database and for changing the structure of the structure of the database);
(3)Possibly a set of integrity constraints,which ensures that the data is accurate.(A set of integrity rules, which ensures the data is accurate.ppt中)
11 Discuss the main types of data model.
object-based data models 、record-based data models、physical data models.
Some of the more common types of object-based data models are:Entity-Relationship; Semantic;Functional;Object-Oriented.
There are three principal types of record-based logical data model:The relational data model,the network data model,and the hierarchical data model.