数据库原理与SQL汉化复习指南：应用与设计

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In all but the simplest system development projects, the step from user requirements to

database design is too big. Accordingly, the development team proceeds in two steps.

First, the team creates a data model from the requirements statements and then

transforms that data model into a database design. You can think of a data model as a

blueprint that is used as a design aid on the way to a database design, which is the basis

for constructing the actual database in a DBMS product.

在除最简单的系统开发项目之外的所有项目中，从用户需求到数据库设计的步骤跨度都太大了。因此，开发团队

分两个步骤进行。

首先，团队根据需求声明创建数据模型，

然后，将该数据模型转换为数据库设计。

您可以将数据模型视为一个蓝图，该蓝图可以用作数据库设计过程中的设计辅助，这是在DBMS产品中构建实际数

据库的基础。

1.6.3. 数据库重新设计

c. Database Redesign

Database redesign also requires that databases are designed. As shown in Figure 1-22,

there are two common types of database redesign.

该方式还需要设计数据库。如图1-22所示，有两种常见的数据库重新设计类型。

In 1970, a then–little-known IBM engineer named E. F. Codd published a paper in the

Communications of the ACM3 in which he applied the concepts of a branch of

mathematics called relational algebra to the problem of “shared data banks,” as

databases were then known.

The results of this work are now the relational model for databases, and all relational

database DBMS products are built on this model.

1970年，当时名不经传的IBM工程师E.F. Codd在ACM3通讯中发表了一篇论文，其中他将数学上一个称为关系代

数的分支概念应用于“共享数据库”问题

这项工作的结果现在是数据库的关系模型，并且所有关系数据库DBMS产品都建立在该模型上。

Over time, Codd convinced IBM management to develop relational-model DBMS products.

The result was IBM’s DB2 and its variants, which are still very popular today.

Meanwhile, other companies were considering the relational model as well, and by 1980,

several more relational DBMS products had been released. The most prominent and

important of those was Oracle Corporation’s Oracle Database . Oracle Database achieved

success for many reasons, one of which was that it would run on just about any computer

and just about any operating system.

随着时间的流逝，科德说服IBM管理层开发关系模型DBMS产品。结果就是IBM的DB2及其变体，今天仍然非常流

行。

同时，其他公司也在考虑关系模型，到1980年，又发布了更多关系DBMS产品。其中最突出和最重要的是Oracle

Corporation的Oracle Database。 Oracle数据库之所以获得成功，有很多原因，其中之一就是它可以在几乎任何

计算机和任何操作系统上运行。

1.8.3. 关系后发展

c. Post-Relational Developments

By 1990, some vendors had developed object-oriented DBMS (OODBMS or ODBMS)

products. These products were designed to make it easy to store the data encapsulated in

OOP objects.

Several special-purpose OODBMS products were developed, and Oracle added OOP

constructs to Oracle to enable the creation of a hybrid (混合) called an object-relational

DBMS.

到1990年，一些供应商已经开发了面向对象的DBMS（OODBMS或ODBMS）产品。这些产品旨在简化存储在

OOP对象中的数据的存储。

也开发了几种专用的OODBMS产品，并且Oracle向Oracle添加了OOP构造，以支持创建对象关系DBMS。

OODBMS never caught on, and today that category(类别) of DBMS products is fading

away.There were two reasons for their lack of acceptance.

First, using an OODBMS required that the relational data be converted from relational

format to object-oriented format. By the time OODBMS emerged, billions upon billions of

bytes of data were stored in relational format in organizational databases. No company

was willing to undergo the expensive travail of converting those databases to be able to

use the new OODBMS.

Second, object-oriented databases had no substantial advantage over relational databases

for most commercial database processing. As you will see in the next chapter, SQL is not

object oriented. But it works, and thousands of developers have created programs that use

it.

Conclusion: Without a demonstrable advantage over relational databases, no organization

was willing to take on the task of converting its data to OODBMS format.

OODBMS从未流行开来，如今，DBMS产品的类别（类别）正在逐渐消失。它们缺乏接受的原因有两个。

首先，使用OODBMS要求将关系数据从关系格式转换为面向对象的格式。到OODBMS出现时，数十亿亿字节的

数据以关系格式存储在组织数据库中。没有一家公司愿意为将这些数据库转换为能够使用新的OODBMS而付出昂

贵的代价。

其次，对于大多数商业数据库处理而言，面向对象的数据库相比关系数据库并没有实质性的优势。正如将在下一

章中看到的那样，SQL不是面向对象的。但是它有效，成千上万的开发人员创建了基于它的程序。

结论：在关系数据库上没有明显优势的情况下，没有组织愿意承担将其数据转换为OODBMS格式所带来的代价。

Meanwhile, the Internet took off. By the mid-1990s, it was clear that the Internet was one

of the most important phenomena in history. It changed, forever, the ways that customers

and businesses relate to each other.

Early Web sites were nothing more than online brochures(小册子), but within a few years,

dynamic（动态） Web sites that involved querying and processing databases began to

appear.

However, one substantial problem existed. HTTP（Hypertext Transfer Protocol ） is a

stateless protocol（无状态协议）; （进一步解释何谓无状态协议）a server receives a request

from a user, processes the request, and then forgets about the user and the request. Many

database interactions are multistage（多级）. A customer views products, adds one or

more to a shopping cart, views more products, adds more to the shopping cart, and

eventually checks

out. A stateless protocol cannot be used for such applications.

同时，互联网开始腾飞。到1990年代中期，互联网已明显的成为历史上最重要的现象之一。它永远改变了客户和

企业之间相互联系的方式。

早期的网站只不过是网上小册子，而是在短短几年内，出现了涉及查询和处理数据库的动态网站。

但是，存在一个实质性的问题。 HTTP（超文本传输协议）是无状态协议；服务器收到用户的请求，处理该请

求，然后忘记用户和该请求。然而许多数据库交互是多阶段的。客户查看产品，将一个或多个添加到购物车，查

看更多产品，将更多添加到购物车，最后结帐。无状态协议不能用于此类应用程序。

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AshleyK

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数据库原理与SQL汉化复习指南：应用与设计

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