Oracle 11gR2数据库概念入门指南

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Oracle Database Concepts 11gR2（11.2）是一本权威的官方指南，专为刚接触Oracle数据库的新手设计。该版本发布于2011年9月，由Oracle公司及其关联方享有版权。主要作者包括Lance Ashdown和Tom Kyte，他们共同撰写了这一重要的教育资源。书中汇集了多位专家的贡献，如Drew Adams、David Austin等，这些专业人士确保了内容的专业性和实用性。本书涵盖了Oracle数据库的核心概念，包括但不限于数据库体系结构、数据模型、SQL语言、存储管理、安全性、性能优化、备份与恢复以及事务处理等方面。对于理解Oracle数据库的基础操作原理、设计最佳实践和解决日常问题有着不可或缺的作用。它不仅介绍了基本的概念和技术，还提供了大量的实例和案例，帮助读者逐步掌握Oracle 11gR2的各项功能。在使用上，Oracle Database Concepts 11gR2强调了许可证协议的重要性，规定了使用和披露的限制，保护了Oracle的知识产权。除了许可协议中的明确规定外，用户必须遵守相关的法律条款，以合法地使用和分享这份软件及相关文档。对于学习者来说，阅读这本书可以加深对Oracle数据库世界的理解，无论是数据库管理员、开发人员还是系统分析师，都能从中获取宝贵的知识和技能。通过深入学习，读者能够建立起对Oracle数据库的坚实基础，从而更好地应对实际工作中的挑战。 Oracle Database Concepts 11gR2是一本极具价值的参考书，对于那些想要步入Oracle数据库技术领域的专业人士，无论是入门学习还是进阶提升，都是不可或缺的参考资料。

xvi

Related Documentation

This manual is intended to be read with the following manuals:

■ Oracle Database 2 Day DBA

■ Oracle Database 2 Day Developer's Guide

For more related documentation, see "Oracle Database Documentation Roadmap" on

page 1-12.

Many manuals in the Oracle Database documentation set use the sample schemas of

the seed database, which is installed by default when you install Oracle Database.

Refer to Oracle Database Sample Schemas for information on how these schemas were

created and how you can use them.

Conventions

The following text conventions are used in this manual:

Convention Meaning

boldface Boldface type indicates graphical user interface elements associated

with an action, or terms defined in text or the glossary.

italic Italic type indicates manual titles, emphasis, or placeholder variables

for which you supply particular values.

monospace

Monospace type indicates commands within a paragraph, URLs, code

in examples, text that appears on the screen, or text that you enter.

About Relational Databases

1-2 Oracle Database Concepts

■ Hierarchical

A hierarchical database organizes data in a tree structure. Each parent record has

one or more child records, similar to the structure of a file system.

■ Network

A network database is similar to a hierarchical database, except records have a

many-to-many rather than a one-to-many relationship.

The preceding database management systems stored data in rigid, predetermined

relationships. Because no data definition language existed, changing the structure of

the data was difficult. Also, these systems lacked a simple query language, which

hindered application development.

Relational Model

In his seminal 1970 paper "A Relational Model of Data for Large Shared Data Banks,"

E. F. Codd defined a relational model based on mathematical set theory. Today, the

most widely accepted database model is the relational model.

A relational database is a database that conforms to the relational model. The

relational model has the following major aspects:

■ Structures

Well-defined objects store or access the data of a database.

■ Operations

Clearly defined actions enable applications to manipulate the data and structures

of a database.

■ Integrity rules

Integrity rules govern operations on the data and structures of a database.

A relational database stores data in a set of simple relations. A relation is a set of

tuples. A tuple is an unordered set of attribute values.

A table is a two-dimensional representation of a relation in the form of rows (tuples)

and columns (attributes). Each row in a table has the same set of columns. A relational

database is a database that stores data in relations (tables). For example, a relational

database could store information about company employees in an employee table, a

department table, and a salary table.

Relational Database Management System (RDBMS)

The relational model is the basis for a relational database management system

(RDBMS). Essentially, an RDBMS moves data into a database, stores the data, and

retrieves it so that it can be manipulated by applications. An RDBMS distinguishes

between the following types of operations:

■ Logical operations

In this case, an application specifies what content is required. For example, an

application requests an employee name or adds an employee record to a table.

■ Physical operations

See Also:

http://portal.acm.org/citation.cfm?id=362685

for an

abstract and link to Codd's paper

About Relational Databases

Introduction to Oracle Database 1-3

In this case, the RDBMS determines how things should be done and carries out the

operation. For example, after an application queries a table, the database may use

an index to find the requested rows, read the data into memory, and perform

many other steps before returning a result to the user. The RDBMS stores and

retrieves data so that physical operations are transparent to database applications.

Oracle Database is an RDBMS. An RDBMS that implements object-oriented features

such as user-defined types, inheritance, and polymorphism is called an

object-relational database management system (ORDBMS). Oracle Database has

extended the relational model to an object-relational model, making it possible to store

complex business models in a relational database.

Brief History of Oracle Database

The current version of Oracle Database is the result of over 30 years of innovative

development. Highlights in the evolution of Oracle Database include the following:

■ Founding of Oracle

In 1977, Larry Ellison, Bob Miner, and Ed Oates started the consultancy Software

Development Laboratories, which became Relational Software, Inc. (RSI). In 1983,

RSI became Oracle Systems Corporation and then later Oracle Corporation.

■ First commercially available RDBMS

In 1979, RSI introduced Oracle V2 (Version 2) as the first commercially available

SQL-based RDBMS, a landmark event in the history of relational databases.

■ Portable version of Oracle Database

Oracle Version 3, released in 1983, was the first relational database to run on

mainframes, minicomputers, and PCs. The database was written in C, enabling the

database to be ported to multiple platforms.

■ Enhancements to concurrency control, data distribution, and scalability

Version 4 introduced multiversion read consistency. Version 5, released in 1985,

supported client/server computing and distributed database systems. Version 6

brought enhancements to disk I/O, row locking, scalability, and backup and

recovery. Also, Version 6 introduced the first version of the PL/SQL language, a

proprietary procedural extension to SQL.

■ PL/SQL stored program units

Oracle7, released in 1992, introduced PL/SQL stored procedures and triggers.

■ Objects and partitioning

Oracle8 was released in 1997 as the object-relational database, supporting many

new data types. Additionally, Oracle8 supported partitioning of large tables.

■ Internet computing

Oracle8i Database, released in 1999, provided native support for internet protocols

and server-side support for Java. Oracle8i was designed for internet computing,

enabling the database to be deployed in a multitier environment.

■ Oracle Real Application Clusters (Oracle RAC)

Oracle9i Database introduced Oracle RAC in 2001, enabling multiple instances to

access a single database simultaneously. Additionally, Oracle XML Database

(Oracle XML DB) introduced the ability to store and query XML.

■ Grid computing

Schema Objects

1-4 Oracle Database Concepts

Oracle Database 10g introduced grid computing in 2003. This release enabled

organizations to virtualize computing resources by building a grid infrastructure

based on low-cost commodity servers. A key goal was to make the database

self-managing and self-tuning. Oracle Automatic Storage Management (Oracle

ASM) helped achieve this goal by virtualizing and simplifying database storage

management.

■ Manageability, diagnosability, and availability

Oracle Database 11g, released in 2007, introduced a host of new features that

enable administrators and developers to adapt quickly to changing business

requirements. The key to adaptability is simplifying the information infrastructure

by consolidating information and using automation wherever possible.

Schema Objects

One characteristic of an RDBMS is the independence of physical data storage from

logical data structures. In Oracle Database, a database schema is a collection of logical

data structures, or schema objects. A database schema is owned by a database user

and has the same name as the user name.

Schema objects are user-created structures that directly refer to the data in the

database. The database supports many types of schema objects, the most important of

which are tables and indexes.

Tables

A table describes an entity such as employees. You define a table with a table name,

such as

employees

, and set of columns. In general, you give each column a name, a

data type, and a width when you create the table.

A table is a set of rows. A column identifies an attribute of the entity described by the

table, whereas a row identifies an instance of the entity. For example, attributes of the

employees entity correspond to columns for employee ID and last name. A row

identifies a specific employee.

You can optionally specify rules for each column of a table. These rules are called

integrity constraints. One example is a

NOT NULL

integrity constraint. This constraint

forces the column to contain a value in every row.

Indexes

An index is an optional data structure that you can create on one or more columns of a

table. Indexes can increase the performance of data retrieval. When processing a

request, the database can use available indexes to locate the requested rows efficiently.

Indexes are useful when applications often query a specific row or range of rows.

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