Oracle Database 10g OCP Certification All-in-One Exam Guide.pdf

PART I

Oracle Database 10 g

Administrative I Exam

■ Chapter 1 Basic Oracle Concepts

■ Chapter 2 Installing Oracle Database 10 g

■ Chapter 3 Creating an Oracle Database

■ Chapter 4 Interfacing with the Oracle Database

■ Chapter 5 Managing Oracle Processes

■ Chapter 6 Managing Oracle Storage Structures

■ Chapter 7 Administering Users

■ Chapter 8 Managing Database Objects

■ Chapter 9 Manipulating Database Data

■ Chapter 10 Programming Oracle with PL/SQL

■ Chapter 11 Securing the Database

■ Chapter 12 Conﬁ guring Oracle Networking

■ Chapter 13 Managing Shared Servers

■ Chapter 14 Managing Database Performance

■ Chapter 15 Monitoring Oracle

■ Chapter 16 Managing Undo

■ Chapter 17 Dealing with Locking

■ Chapter 18 Conﬁ guring the Database for Backup and Recovery

■ Chapter 19 Backing Up Oracle Databases

■ Chapter 20 Recovering Oracle Databases

■ Chapter21 Managing Globalization in Oracle Databases

CHAPTER 1

Basic Oracle Concepts

In this chapter you will learn

• What a database is and what makes a database relational

• What SQL is

• Which database objects are supported in Oracle 10 g

• What a database administrator does

• How the Oracle database fits into the Oracle product family

Oracle Database 10 g OCP Certification All-in-One Exam Guide

Someone once said that the best place to start is at the beginning. With Oracle, that

means understanding where the idea of a relational database management system

(RDBMS) came from and what a database is—in computer and everyday terms. Even

though the material presented here may not be directly tested on the exam, this is

assumed knowledge, however, so a quick read is probably a good idea.

Introduction to Databases

and the Relational Model

In one form or another, databases have always been around, though their exact shape

was not always easily recognizable. As long as some form of data had to be stored,

there was always a method of storing it.

Databases, in their most simple form, are a mechanism for storing data. The data

can be logical, like the values stored in a computer program, or may be physical, like

a file or receipt. You probably have databases in existence all around you, but you

may not see them as such. For example, the shoebox in which you’ve placed your tax

receipts for the accountant is a database of your annual expenses. When you open a

file cabinet and take out a folder, you are accessing a database. The content of the file

folder is your data (e.g., your credit card statements, your bank statements, invoices,

purchase orders, etc.). The file cabinet and drawers are your data storage mechanisms.

Before the advent of computers, all data was stored in some easily recognizable

physical form. The introduction of computers simply changed the data from a physical

form that you can touch and feel to a digital form that is represented by a series of 1’s

and 0’s. Does the information that you display for an expense report on the computer

screen differ greatly from the same information in the hard-copy version of the expense

form? Perhaps the information is laid out differently than on the screen, but the key

elements—who was paid, what amount, how much was the tax, what was the purpose

of the expense, and so on—are all the same.

In looking at a database and its most basic set of characteristics, the following

points hold true:

• A database stores data. The storage of data can take a physical form, such as

a filing cabinet or a shoebox.

• Data is composed of logical units of information that have some form of

connection to each other. For example, a genealogical database stores

information on people as they are related to each other (parents, children, etc.).

• A database management system (DBMS) provides a method to easily retrieve,

add, modify, or remove data. This can be a series of filing cabinets that are

properly indexed, making it easy to find and change what you need, or a

computer program that performs the same function.

Chapter 1: Basic Oracle Concepts

When data began to move from a physical form to a logical form using computers,

different theoretical versions of systems to manage data evolved. Some of the more

common database management systems in use over the last 50 years include the

hierarchical, network, and relational. Oracle is a relational database management system

(RDBMS).

The Relational Model of Databases

The relational model for database management systems was proposed in the June

1970 issue of Communications of the ACM— the Association of Computing Machinery

journal—by Dr. E.F. Codd, an IBM researcher, in a paper called “A Relational Model

of Data for Large Shared Data Banks.” For its time it was a radical departure from

established principles because it stated that tables that have related data need not

know where the related information is physically stored. Unlike previous database

models, including the hierarchical and network models, which used the physical

location of a record to relate information between two sets of data, the relational

model stated that data in one table needed to know only the name of the other table

and the value on which it is related. It was not necessary for data in one table to keep

track of the physical storage location of the related information in another.

NOTE The full text of Dr. E.F. Codd’s paper “A Relational Model of Data for

Large Shared Data Banks” can be found in the classics section of the ACM

web site at www.acm.org/classics/nov95/toc.html.

The relational model broke all data down into collections of objects or relations

that store the actual data (i.e., tables). It also introduced a set of operators to act on

the related objects to produce other objects (i.e., join conditions to produce a new

result set). Finally, the model proposed that a set of elements should exist to ensure

data integrity so that the data would be consistent and accurate (i.e., constraints). Codd

proposed a set of twelve rules that would allow designers to determine if the database

management system satisfied the requirements of the relational model. Although no

database today satisfies all twelve rules (because the database would run very slowly if

it did, since theory is not always the same as practice), it is generally accepted that any

RDBMS should comply with most of them.

The essence of the relational model is that data is made up of a set of relations.

These relations are implemented as two-dimensional tables with rows and columns

as shown in Figure 1-1. In this example, the Customers table stores information about

clients we deal with—their customer ID, their company name, their address, and so on.

The Orders table stores information about the client orders (but not the order line

items—these are in another table), including the order data, the method of payment,

the order date, and the ship date. The CustomerID column in both tables provides the

relationship between the two tables and is the source of the relation. The tables

themselves are stored in a database that resides on a computer. The physical locations

of the tables need not be known—only their names.

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