INTRODUCTION TO ORACLE SQL

OBJECTIVES

• At the end of this module, you should be able to:

• Know what Data is and what a Database is.

• Understand Database Management Systems and

Relational Databases.

• Understand the use of SQL and Oracle SQL.

WHAT IS ORACLE?

ORACLE is a relational database management software.

DATA is a collection of facts, such as values, numbers,

words, measurements, observations or the

descriptions of things.

• A DATABASE refers to an organized mechanism for

storing, managing and retrieving data-information. A

database performs these typical functions through

the use of tables.

• If you are familiar with spreadsheets like Microsoft

Excel, you’re probably already accustomed to

storing data in tabular form. You would just move

further from spreadsheets to databases.

• A customer database for example, would contain the

customer's ID, first name, last name, and email

address, and each row would contain an individual

customer’s data.

• A DATABASE MANAGEMENT SYSTEM (DBMS) -also called a database

manager- is a program that lets one or more

computer users, create and access data in a

database. The DBMS manages user requests so that

users and other programs are free from having to

understand where the data is physically located.

• By definition, a DBMS is a software package with

computer programs that control the creation,

maintenance, and the use of databases, allowing

organizations to conveniently develop databases for

various uses. A DBMS would also allow different user

programs to concurrently access the same database.

• Database Applications are used in banks, schools,

airlines, hospitals, cooperate offices etc.

• When we make flight reservations online, we are

providing information that is entered into a

database management system. When we buy at the

supermarket and get a receipt, that sale is recorded

in a database.

• On a more personal level, our personal computer can

have its own database management system. We may

have Microsoft Excel sheets that contain mountains

of data. Any time we fill up a sheet with data and run

queries to find and analyze data in different ways,

we are accessing a database management system.

• Our phonebook is database. When we add contacts,

delete contacts and search for friends phone

numbers on our phonebook, we are simply accessing

a database.

• A RELATIONAL DATABASE MANAGEMENT SYSTEM stores up all its

information in tables but it also stores information

about the relationship between its tables. In a

relational database management system, data can be

accessed or reassembled in many different ways

without having to change the table forms.

• To communicate with a RDBMS, we need a language.

• STRUCTURED QUERY LANGUAGE which we call SQL -pronounced in

the industry as sequel- is an international standard

language for communicating with relational

databases.

• SQL can create, delete, and change data in tables. It

can also input data into tables and remove data. It is

a data handling language.

• Just like any other language, SQL has dialects and

ORACLE SQL is the dialect that communicates with

the Oracle Database. Other dialects include: MySQL,

PLSQL, Microsoft SQL etc.

REVISION QUESTIONS

1. Explain the use of data

2. What are databases and how are they used in

today’s society.

3. What do the following abbreviations stand for:

• DBMS.

• RDBMS.

• SQL.

4. Compare a Microsoft Excel spread sheet with a

Database.

INSTALLATION AND

CONFIGURATION

OBJECTIVES

At the end of this module, students should be able to:

• Install Oracle Express Edition on their personal

computer and configure it.

• Have a fair understanding of the database home

page

INSTALLATION AND CONFIGURATION

• Oracle express edition is a free small edition of the

Oracle database. It uses a browser based interface to

create tables and other database objects, to generate

reports and to build web-based applications.

RUN INSTALLATION

• Now with Oracle Express Edition already installed

on your personal computer, do the following:

• Click the start button then

• Click Oracle Express Edition 10g/11g,

• Select Go To database home page.

Fig 1.1

• We must first log in as an administrator, so when the

LOGIN window is displayed in your web browser:

• Enter USERNAME as SYSTEM

• Enter PASSWORD as the password we choose during

installation.

• Click on LOGIN.

DATABASE HOMEPAGE

• The Database homepage will open if you input the

correct password in the LOGGIN window and this

Homepage has four large icons on it.

• Administration - is used for the sole aim of

management. It manages user accounts, manages

memory, manages storage and monitors sessions.

• Object browser- is used to create tables and other

schema objects and to browse the schema objects.

• SQL - uses the SQL command line as a tool to run

SQL commands. The SQL script is used to edit and

run script files, while the query builder is used in

building SQL queries using a graphical user

interface.

• Utilities - is used to load and unload data, to

generate data definition language, object reports and

to recycle.

DATABASE LOGIN

• You are now logged in as system, so the user name

displayed at the top of the page is system. The next

thing to do is to unlock the sample user accounts

where you would have access to some tables and

other schema objects.

• Oracle Express Edition comes with a fictional human

resource department’s database and that database

has a good number of schema objects. The user

name for the human resource department is HR, and

it is locked by default, so you would have to UNLOCK it.

To do this;

• Click on the administration icon

• Click database users

• Click the HR icon

• Under the database users, enter a password of

choice and confirm the password.

• Select Unlocked in the account status

• Under Roles, you ensure that Connect and Resource

are enabled

• Click Alter User.

• Now click Logout at the upper right corner.

Click LOGIN again.

To Login as HR as our USER NAME

• Enter the chosen password.

• Click LOGIN.

COMMAND WINDOW

You would be entering all SQL statements in the SQL

enter command window, so let us zoom in on that

window.

• On the Home-Page:

• Click the SQL icon

• Select SQL Command line and then

• Click Enter Command.

• This opens the SQL Command Window and on this

window we can create, edit, view run and delete SQL

Commands.

• The SQL Window contains a Command Editor used

to enter and edit command lines, and a Display Pane.

• The AUTO COMMIT check box is checked to enable

an auto-commit of all SQL commands. The DISPLAY

drop down is used to determine the number of rows

to be displayed in the display pane.

• The SAVE button is used to save a SQL statement

giving it a file name and a description. The RUN

button is used to run or execute a SQL command.

• On the Display Pane, we can either view the result of

a SQL command, or view a list of saved SQL

commands. The History Tab would display previous

transaction and the Describe Tab is used when we

describe schema objects.

REVISION QUESTIONS

1. What are the four Icons on the Homepage?

2. What are their respective functions?

3. Where is the RUN and SAVE button located on the

Command Window?

4. What are they used for?

5. Where are SQL Commands entered?

RETRIEVING DATA USING THE SQL

SELECT STATEMENT.

OBJECTIVES

At the end of this module, students should be able to:

1. List the capabilities of the SQL select statement.

2. Execute a basic select statement.

3. Describe how Schema objects work.

A SIMPLE SELECT STATEMENT

• A basic SELECT statement is the simplest SQL statement.

It is used to query a database and it has three basic

functions. It:

• PROJECTS - chooses the column to be returned by the

query block,

• SELECTS - chooses the rows to be returned by the query

block.

• JOINS - brings together data from different tables for

display.

• The SELECT keyword is always used with the FROM

keyword.

FORMAT:

SELECT *

FROM table_name;

• When we want to display all the rows in all the

columns in a table, we simply say:

FIG 2.1

• This simple select statement will display all the data

in the employees table. However when we want to

display specific columns in the table we do so by

listing these column names in the SELECT statement

and separating each column name with a comma.

FORMAT:

SELECT column_name1, column_name2

FROM table_name;

EXAMPLE

• Notice that this query returns the employee_id,

first_name and the last_name column for all the rows

in the employees table.

COLUMN ALIASES

• When columns are displayed in the display pane by a

SELECT statement, you would notice that the name of

each column is used as the column heading.

However this column names could be completely

vague and meaningless.

• At such times, you may want to rename the column

heading with a more meaningful name. You do this

by using a column alias.

• A column alias is placed in the SELECT clause just beside

the column name and the AS keyword is introduced.

FORMAT:

SELECT column_name AS alias

FROM table_name;

EXAMPLE

• You would notice that when a column alias is used,

the column heading changed from employee_id to

staff code.

RULES

• A column alias could be used with or without the AS

keyword.

• When writing a column alias, that contains spaces, it

is necessary to quote them in double quotation

marks “”.

DESCRIBE

• The DESCRIBE keyword is used to show the

structure of a Schema object. It displays the

column_names, data-type and all other meta data.

FORMAT:

DESCRIBE table_name;

EXAMPLE:

• The oracle server returns a detailed description of

the structure of the specified table including the

column names and any constraint details.

REVISION QUESTION

1. What are the basic functions of a SELECT

statement?

2. Write a SELECT statement to display the content

of the jobs table.

3. Write a SELECT statement to display the

first_name column of the employees table.

4. DESCRIBE the locations table.