塔城大学-塔城大学
Chapter 1 Introduction- Review questions
1.1 Discuss the meaning of
each of the following terms
(a)
data
数据
For
end
users,
this
constitutes
all
the
different
values
connected
with
the
various
objects/entities that are of concern to
them.
（数据是用户所关心的不同实体或者对象的所
有取值的集合）
(b)
database
数据库
A shared collection
of logically related data (and a description of
this data), designed to
meet the
information needs of an organization.
（数据库是为 了满足一个企业的信息需求而设
计的可以共享的，逻辑上相关的数据以及数据的描述的集
合）
(c)
database management system DBMS
数据库管理系统
A software system that: enables users
to define, create, and maintain the database and
provides controlled access to this data
base.
（
数据库管理系统是一个软件系统，它让用户能
够方便地定义、创建和管理数据库，并提供对数据库的受限制的访问
）
(d)
data independence
（数据独立性）
This
is essentially the separation of underlying file
structures from the programs that
operate on them, also called program-
data independence.
（数据独立性就是数据结构与对这
些数据进行处理的程序之间的分离，也称程序
-
数据独立性）
(e)
views.
（视图）
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.
（视图是虚 表，数据库中并
不保存视图表，但它是由
DBMS
在对视 图进行存取时从基本表导出）
1.4
Describe the five components of the DBMS environment and discuss how they
relate
to each other.
(1)
Hardware
（硬件）
:
The
computer
system(s)
that
the
DBMS
and
the
application
programs
run on. This can range from a single PC, to a
single mainframe, to a network
of
computers.
（硬件包括用来运行
DBMS
以及应用程 序的计算机系统，
可以是单个
PC
机，
可
以是单台主机，也可以计算机网络。）
(2)
Software
（
软件）
:
The DBMS software and the application programs,
together with the
operating
system,
including
network
software
if
the
DBMS
is
being
used
over
a
network.
（软件包括
DBM S
，应用程序，操作系统以及网络软件）
(3)
Data
（数据）
:
The
data
acts
as
a
bridge
between
the
hardware
and
software
components and the human components. As
we?ve already said, the database contains
both the operational data and the
meta-
data (the ?data about data?).
（数 据是计算机软
件、硬件以及用户之间的桥梁，数据库中不仅包括数据，还包括数据字典）
(4)
P
rocedures
（规则与过程）
:
The
instructions and rules that govern the design and
use of
the
database.
This
may
include
instructions
on
how
to
log
on
to
the
DBMS,
make
backup copies of the
database, and how to handle hardware or software f
ailures.
（规
则与过程指导设计和使用数据库，
包括登陆
DBMS
，
数据库备份，
硬件与软件失败 处理等。
）
（
5
）
People
（人员）
:
This
includes
the
database
designers,
database
administrators
(DBAs),
application programmers, and the end-users.
（包括数据库设计者，数据库管理员，
应用程序员以及最终用户）
1.7
Discuss the advantages and disadvantages of DBMSs.
（
DBMS
的优点）
Some advantages of the database
approach include
：
control
of data redundancy,
data consistency,
sharing of data,
and improved security and integrity.
优点：可控的冗余度，数据的共享性，提高了数据的安全性和完整性。
Some disadvantages
include
：
complexity,
cost, reduced performance, and higher impact of a
failure.
缺点：
复杂性，高费用，
降低的性能，
一旦出现问题带来的后果的严重性
Chapter 2
?
1.
Describe the ANSI-
SPARC three-level architecture, and discuss the
advantage of this architecture.(
描述三级体系结构，并讨论该结构的优点
)
External
level:
The users? view of the database. This level describes that part of the
database that is
relevant to each user.
Conceptual
level:
The community view of the database. This level describes what data
is stored in the database and the
relationships among the data.
Internal
level:
The physical representation of the database on the computer. This
level
describes how the data is stored in the database.
There
are
two
mappings
in
the
the
ANSI-SPARC
three-level
architecture:
External/Conceptual
mapping
and
Conceptual/Internal
mapping.
External/Conceptual
mapping enable the DBMS to map the data
in the user?s view on to the relevant part of the
conceptual
schema.
Conceptual/Internal
mapping
enable
the
DBMS
to
find
the
actual
record or combination of records in
physical storage that constitute a Logical record
in
the conceptual schema, together with
any constraints to be enforced on the operations
for that logical record.
A
major advantage for the three-level
archite
cture is to separate each user?s view of
the databases from the way the
database is physically represented and then to
provide
data
independence,
which
means
that
upper
levels
are
unaffected
by
changes
to
lower
levels.
There are
two kinds of data independence:
logical data independence and physical
data
independence.
?
2. What is logical data independence
（
什么是数据库的逻辑独立性）
?
Logical data independence refers to the
immunity of the external schemas to changes
in the conceptual schema.
?
what is physical data independence
（什么是数据库的物理独立性）
?
changes in the internal
schema.
physical
data
independence
refers
to
the
immunity
of
the
conceptual
schemas
to
?
3. What is data model? Describe the components of data model.(
什
么
是数据模型？描述数据模型三要素。
p35)
A
data
model
is
an
integrated
collection
of
concepts
for
describing
data
and
manipulation on
the data, relationships between data, and
constraints on the data.
（数据
模型是一系
列用来描述数据，数据之间的联系，在数据之上所允许的操作的集合以及约束条件
的集合
。）
?A data model has three
components
三要素
:
–
a structural part(
结构要素
): A description of the data and relationships between the
data
–
a manipulative part(
操作要素
): the operations allowed
–
a set of integrity rules.
完整性约束规则
?
4. Discuss the main types of data model.(p35)
(1)Object-Based
data
models:
Object- Based
data
models
use
concepts
such
as
entities, attributes, and
relationships. Some more common types are Entity-
Relationship,
Semantic, Functional,
Objected-Oriented.
(2)Record-Based data
models
（
Logical data model
）
:
In
this
model,
the
database
consists of a number of fixed-format
records possibly of differing types. Each record
type defines a fixed number of fields,
each typically of a fixed length.
There are three types of record-based
data models:
Hierachical data
model
层次数据模型
Network data
model
网状数据模型
Relational
data mode
关系数据模型