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Beginning with SQL


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iii

Beginning

with SQL

A Simplified Approach

Dr. Parteek Bhatia

Associate Professor

Department of Computer Science and Engineering

Thapar University, Patiala, India

EDUCREATION PUBLISHING (Since 2011)

www.educreation.in


iv


v

Preface

It is by now a proven fact that automation and data applications bring about transparency in all

spheres of life. There is certainly a growing demand for database experts in the country. This book

is intended to fill this gap. This book on SQL has been specially designed to better equip the

learners for their University examination and placement interviews. This book is aimed at

beginners, but it will give you enough information to get mastery on the subject.

Most software written today relies on relational databases such as

Oracle/MySQL/DB2/SQL Server etc. In this book, you'll learn the SQL

language using Oracle, i.e., the most widely used Database Software in the

world.

This book covers the basics of database fundamentals, non procedural nature

of SQL, Creation of tables, performing insert, update, delete and retrieve

operations on tables, joining of tables, grouping of data, inbuilt functions, sub

queries, database objects like view, sequence and indexes. These concepts are

covered through lot of examples to make the learning fun and exciting.

The main strength of the book is explanation with the practical examples so that

learners can grasp the contents easily. Each chapter contains Brain Storming

Session on number of practical problems and Hands-On Session to promote

learning by doing approach. This book provides a good number of multiple

choice questions for preparation of placements, quizzes and competitive exams.

Your suggestions for further improvement of the book are very valuable and kindly mail your

suggestions at [email protected].

I hope that you enjoy learning from this book as much as I enjoyed writing it.

Dr. Parteek Bhatia

2017


mailto:[email protected]

vi

Acknowledgements

Beginning with SQL is an evolving project, which could not have been possible

without the contribution and support of scores of people.

I would like to express here, my gratitude to the students of Thapar University,

Patiala; DAV College, Amritsar and from other institutes to whom I got the

opportunity to interact during different sessions. They provided the much

needed motivation without which this book would have been impossible.

I am deeply grateful for the guidance and support provided by my mentors Mr.

M.L. Aeri, Mr. O.P. Bhardwaj, Dr. R.K. Sharma, Dr. Seema Bawa, Dr.

Maninder Singh and my friends Dr. Amandeep Gupta and Dr. Deepak Garg

during writing of this book.

I owe much to the Department of Computer Science and Engineering,

Thapar University for providing all the resources that helped me to attain the

requisite level of excellence to complete this book.

My family members stood by me firm as rocks all through the period when

the book was being researched and written. I acknowledge here the debt of

gratitude I owe my parents, Mr. Ved Kumar; Mrs. Jagdish Bhatia and Mr Dalip

Singh and Mrs Joginder Kaur for their constant encouragement. And lastly I

would like to thank my wife Dr. Sanmeet Kaur, and sons Rahat and Rishan for

their forbearance and the patience they displayed for such an extended period of

time, without which I would never have been able to complete the task. I would

like to acknowledge contribution of my son Rahat in preparing the index of the

book.


vii

About the Author

Dr. Parteek Bhatia is Associate Professor in the

Department of Computer Science and Engineering at

Thapar University, Patiala. He has more than eighteen

years of academic experience, including six years at

D.A.V College Amritsar. He has earned his B.Tech

from SLIET and MS from BITS Pilani. He has

completed his Ph.D on "UNL Based Machine

Translation System for Punjabi Language" from Thapar

University. He has published more than 75 research

papers and articles in Journals, Conferences and

Magazines of repute. His research work with UNDL

foundation, Geneva, Switzerland involved participation

in Advanced UNL School at Alexandria, EGYPT in

2012 and at Geneva, Switzerland in 2013 and 2014. He

is a winner of Gold Medal at International competition UNL Olympiad II, UNL

Olympiad III and UNL Olympiad IV conducted by UNDL Foundation Geneva

in year 2013 and 2014. He has authored six books including Simplified

Approach to DBMS, Simplified Approach to Visual Basic and Simplified

Approach to Oracle. He has successfully completed research Project on

Development of Indradhanush: An Integrated WordNet for Bengali, Gujarati,

Kashmiri, Konkani, Oriya, Punjabi and Urdu Sponsored By Department of

Information Technology, Ministry of Communication and Information

Technology, Govt. of India. He is acting as Principle Investigator for DST

sponsored research project on “Automatic generation of Sign Language from

Hindi Text for Communication and Education of Hearing Impaired People”. He

is working as working as Co-PI for development of Mini MOOCS under a

research project funded by Royal Academy of Engineers (UK). His research

interests are NLP, Machine Learning and Human Computer Interaction.

sites.google.com/site/parteekbhatia

[email protected]


viii

Dedicated to

My Parents Mr. Ved Kumar & Mrs. Jagdish Bhatia

Supportive Wife Dr. Sanmeet Kaur

Loving Sons Rahat & Rishan

By Parteek Bhatia…


ix

Contents

CHAPTER 1: BEGINNING WITH SQL 1-7

1.1 Introduction to Structured Query Language

1.2 SQL Fundamentals

1.2.1 Data Definition Language (DDL) statements

1.2.2 Data Manipulation Language (DML) statements

1.2.3 Data Control Language (DCL)

1.2.4 Transaction Control Language (TCL) statements

1.3 Data types of SQL

CHAPTER 2: INVOKING SQL*PLUS 8-15

2.1 SQL*PLUS Interface

CHAPTER 3: PERFORMING BASIC OPERATIONS OF

DATABASE WITH SQL 16-26

3.1Beginning with Performing Basics operations of database

CHAPTER 4: BASIC SELECT STATEMENT 27-58

4.1 Databases used in examples

4.2 SELECT Statement

4.3 Use of Wildcard(*) character

4.4 Elimination of Duplication with DISTINCT Clause

4.5 The Oracle table „DUAL‟

4.6 Limiting Rows

4.7 Special Operators

4.8 Working with NULL Values

4.9 ORDER BY Clause

4.10 Changing Column Headings with Column Aliases


x

4.11 Column Concatenation

4.12 Pattern matching

4.13 Using Set Operators

4.13.1 Union operator

4.13.2 Union All Operator

4.13.3 Intersect operator

4.13.4 Minus operator

4.14 Oracle‟s Pseudo columns

4.14.1 CURRVAL and NEXTVAL

4.14.2 ROWID

4.14.3 Rownum

4.15 Accepting Values at Runtime

CHAPTER 5: INBUILT FUNCTIONS 59-84

5.1 Functions in SQL*PLUS

5.1.1 Single Row Functions

5.1.2 Multi row or Group Functions in SQL

CHAPTER 6: GROUPING OF DATA 85-95

6.1 Grouping Data with GROUP BY

6.2 Grouping by more than one column

6.3 Restricting Group Results with HAVING clause

CHAPTER 7: JOINING OF TABLES 96-111

7.1 Joining of tables for multiple table Queries

7.2 Types of Joins


xi

7.2.1 Cartesian product

7.2.2 Inner Join

7.2.2.1 Equality Joins

7.2.2.2 Non-Equality Join

7.2.3 Outer Joins

7.2.3.1 Left/Right-Outer join

7.2.4 Self-Join

CHAPTER 8: SUB QUERIES 112-129

8.1 Using a Sub-query to solve a problem

8.2 Types of Subquries

8.2.1 Single-Row Sub queries

8.2.2 Multiple-Row Sub-queries

8.2.3 Multiple-column Subquries

8.3 Correlated Sub-queries

8.4 Using special operators in Sub-queries

8.4.1 EXISTS Operator

8.4.2 ANY Operator

8.4.3 ALL Operator

CHAPTER 9: MANAGING TABLES 130-156

9.1 Introduction to tables

9.2 Structure of table: Design tables before creating them

9.3 Table creation rules

9.4 Create Table Statement

9.5 Creating table from an existing Table9.6 Role of Constraints to

achieve data integrity

9.6.1 Column Constraints


xii

9.6.2 Table Constraints

9.7 Types of Constraints

9.7.1 NOT NULL constraint

9.7.2 Unique constraint

9.7.3 Primary key constraint

9.7.4 Check constraint

9.7.5 Default constraint

9.7.6 Foreign key constraint

9.8 Creating a Table with rows from another table

9.9 Required Permissions to Create a Table

9.10 To display information about Table

9.11 The user_constraints table

9.12 Altering Tables

9.12.1 To ADD new columns

9.12.2 To MODIFY columns

9.12.3 The DROP option

9.12.4 Drop column option

9.13 Removing Tables

9.14 Available tables as Data Dictionary

CHAPTER 10: DATABASE OBJECTS, DCL AND TCL

STATEMENTS 157-177

10.1 Creation of View

10.2 Types of views

10.2.1 Horizontal views

10.2.2 Vertical views

10.2.3 Row/column subset views


xiii

10.2.4 Grouped views

10.2.5 Joined views

10.3.Data Manipulation in View

10.3.1 Updating a view

10.4 Dropping a View

10.5 Views with CHECK Option

10.6 Advantages of views

10.7 Disadvantages of views

10.8 Sequences: Database Object

10.9 Index: Database Object

10.9.1 Uses of Indexing

10.9.2 Types of Indexes

10.9.3 Creation of Simple Duplicate Index

10.9.4 Creation of Composite Duplicate Index

10.9.5 Creation of Simple Unique Index

10.9.6 Creation of Composite Unique Index

10.9.7 Dropping of existing Indexes

10.9.8 Problem Caused by too many Indexes

10.10 Index Guidelines

10.11 Oracle Index schemes

10.12 TRANSACTION CONTROL LANGUAGE

STATEMENTS

10.13 DATA CONTROL LANGUAGE STATEMENTS

10.13.1 GRANT Command

10.13.2 REVOKE Command

10.14 Creation and Management of User Accounts


xiv

10.14.1 Steps to create user

10.14.2 Altering User Account

10.14.3 Deleting User Account

10.15 Oracle Tree Walking

Index 178


Beginning with SQL ________________________________________________________________________

1

Chapter Objectives In this chapter you will learn

Non procedural capabilities of SQL

Classification of SQL statements

Data types of Oracle _________________________________________________________________

1.1 Introduction to Structured Query Language

Structured Query Language usually refereed as SQL, it is a non procedural

language, where a user need not write a program to perform his desired database

task (insert, update, delete and retrieve) but he has to provide his request for the

task in a structured manner to the system and system takes care of his request,

i.e., it process its request and provide the desired result without writing a single

line of code.

In other words, user has to provide the information to computer “what is

require to be perform”, but need not to provide the details about “how to

perform the task”. User does not write the procedure/algorithm/program to get

the result simply he has to provide his request in a structured manner, that‟s why

it is called as Structured Query Language.

While in procedural languages like C, user has to write the

procedure/algorithm/program for task he wishes to execute on the computer.

Even to find the sum of two numbers user has to write the program while in non-

procedural language like SQL user need not to write the program.

Thus, due to non procedural nature of SQL it make it very simple and easy to

use. This is the major reason for the popularity of SQL because it is simple, easy

to use and without writing the programs user is able to perform all database

tasks, i.e., insert, update, delete and retrieve without writing the programs.

01 BEGINNING WITH SQL


Parteek Bhatia ________________________________________________________________________

2

But, this non-procedural nature of SQL has a limitation, it has limited

capabilities, because in non-procedural language we cannot make the use of if

statement, Looping statement etc. and sometimes it is difficult to implement

whole business logic with SQL. To add procedural capabilities to SQL, SQL has

been extended to PL/SQL, i.e., Procedural Language/ Structured Query

Language. PL/SQL has capacities of procedural language, i.e., provision to use

conditional and looping statements etc. with non procedural capabilities of SQL.

In this chapter, we will discuss the basics of SQL while PL/SQL has been

discussed in Chapter 30. In this chapter, SQL statements of most commonly

used database software, i.e., Oracle has been discussed.

1.2 SQL Fundamentals

SQL is a simple and powerful language used to create, access, and manipulate

data and structure in the database. SQL is like plain English, easy to understand

and write. Oracle divides SQL statements into various categories, which are:

Data Definition Language

Data Manipulation Language

Data Control Language.

Transaction Control Language

Embedded SQL statements

1.2.1 Data Definition Language (DDL) statements

DDL statements are used to define, alter, or drop database objects.

The following table gives an overview about usage of DDL statements in

ORACLE:

S.No Need and Usage Example The SQL DDL

statement

1 Create schema objects Creation of table CREATE

2 Alter schema objects Alteration in

structure of table

ALTER

3 Delete schema objects Deletion of whole

table

DROP

4 Rename schema objects Renaming of table RENAME

1.2.2 Data Manipulation Language (DML) statements

Once the tables have been created, the DML statements enable users to query or

manipulate data in existing schemas objects. DML statements are normally the

most frequently used commands. The following table gives an overview about

the usage of DML statements in ORACLE.



3

1.2.3 Data Control Language (DCL)

A privilege or right can either be granted to a user with the help of GRANT

statement. The privileges assigned can be SELECT, ALTER, DELETE,

EXECUTE, INSERT, INDEX etc. In addition to granting of privileges, you can

also revoke (taking it back) it by using REVOKE command.

S.No Need and Usage The SQL DCL

statement

1 Grant and take away privileges and roles GRANT

REVOKE

2 Add a comment to the data dictionary COMMENT

1.2.4 Transaction Control Language (TCL) statements

TCL statements manage the change made by DML statements, and group DML

statements into transactions. The following table gives an overview about the

usage of TCL statements in ORACLE.

S.No Need and Usage The SQL TCL

statement

1 Make a transaction‟s changes permanent COMMIT

2 Undo changes in a transaction, either since

the transaction started or since a savepoint

ROLLBACK

3 Set point to which transaction can be rolled

back

SAVEPOINT

4 Establish properties for a transaction SET

TRANSACTION

1.3 Data types of SQL

At this point, it is necessary to discuss the available data types in the Oracle

database. As we know that information in a database is maintained in the form

S.No Need and Usage The SQL DML

statement

1 Remove rows from tables or views DELETE

2 Add new rows of data into table or view INSERT

3 Retrieve data from one or more tables SELECT

4 Change column values in existing rows of a

table or view

UPDATE


Parteek Bhatia ________________________________________________________________________

4

of tables and each table consists of rows and columns, which stores data, and

therefore this data must have some data type i.e the type of data, which is stored

in a table.

The different data types available in SQL are:

Data types Description

VARCHAR2 Contains variable length text strings of up to 2,000

bytes

CHAR Contains fixed text strings of up to 255 bytes

NUMBER Contains numeric data

DATE Contains date data

RAW Contains binary data of up to 255 bytes

LONG Contains text data of up to 2 gigabytes

LONG RAW Contains binary data of up to 2 gigabytes

ROWID Contains disk location for table rows

BLOB Large binary object

CLOB Large character-based object

NCLOB Large single- or multi byte character-based object

BFILE Large external file

The most commonly used data types are:

char

varchar or varchar2

number

date

long

long raw/ raw

Let us now briefly describe these data types:

Let us now briefly describe these data types:

Char(n) : This data type is used to store character strings of fixed size. The size

of the character string is determined by the numeric value of n. This data type

can hold maximum of 255 characters. When Oracle stores data in a CHAR data

type, it will pad the value stored in the column up to the length of the column as

declared by the table with blanks.



5

For example: If data type of address field is mentioned as CHAR(40) and

address information of a particular record complete in 20 characters, then

remaining 20 characters space is padded with blank characters.

Varchar(n)/Varchar2(n) : This data type is used to store variable length

alphanumeric data. It can store maximum of 2000 characters. In case of varchar

data type, Oracle will not store padded blank spaces if the value stored in a

column defined is less than length of the column as declared by the table with

data type VARCHAR2.

For example: If data type of address field is mentioned as VARCHAR(40) and

address information of a particular record complete in 20 characters, then

remaining 20 characters space is not padded with blank characters and memory

space of 20 characters is used for some other purposes and not wasted as

padded with blank characters.

Number (p,s) : This data type is used to store numbers fixed or floating point

.The precision (p) determines the length of the data while (s), the scale,

determines the number of places after the decimal. The NUMBER data type that

is used to store number data can be specified either to store integers or decimals

with the addition of a parenthetical precision indicator.

For example, if you had a column defined to be data type NUMBER(10,3),

the number 546.3832 would be stored as 546.383, because after the decimal

point we can store 3 digits. Let us consider another data type NUMBER (3,2),

the maximum number stored in this data type is 9.99, because it has a precision

as 3 and scale as 2. It means that the length of data is 3 including 2 after the

decimal point leaving only one before decimal point. Thus, it can accommodate

maximum number 9.99, but it cannot store 10, because it has 2 digits before the

decimal point.

What will be maximum number stored in data type NUMBER (7,3)? The

answer is 9999.999. I hope that you got the logic.

If we do not use scale then the default value is zero and if we don‟t use

precision then by default maximum value stored can be of precision up to 38

digits.

Date : This data type stores date values in a special format internal to Oracle. It

offers a great deal of flexibility to users who want to perform date manipulation

operations. There are also numerous functions that handle date operations more

complex than simple arithmetic. Another nice feature of Oracle‟s method for

data storage is that it is inherently millennium compliant. The default format in

which date is stored is DD-MON-YY. If we want to store date in other format

then we have to use the appropriate functions.


Parteek Bhatia ________________________________________________________________________

6

Long: The developer can declare columns to be of LONG data type, which can

stores up to 2 gigabytes of alphanumeric text data. The values of long data type

cannot be indexed and normal characters functions such as SUBSTR cannot be

applied to long values.

Long Raw/Raw : It is useful to store graphics and sound files when used in

conjunction with LONG to form the LONG RAW data type, which can

accommodate up to 2 gigabytes of data.

Note: A table cannot contain more than one Long column. They cannot be

indexed and no integrity constraints can be applied on them (except for NULL

and NOT NULL constraint).

LOB Type

The LOB (large object) data types BFILE, BLOB, CLOB, and NCLOB allow

storing blocks of unstructured data (such as text, graphic images, video clips,

and sound waveforms) up to four gigabytes in size. And, they allow efficient,

random, piece-wise access to the data.

***

Flashback

______________________________________________________

SQL is a simple and powerful language used to create, access, and manipulate

data and structure in the database. SQL statements into various categories, which

are: Data Definition Language, Data manipulation Language, Transaction

Control Statements and Embedded SQL statements.

DDL statements are used to define, alter, or drop database objects. Once the

tables have been created, the DML statements enable users to query or

manipulate data in existing schemas objects. TCL statements manage the change

made by DML statements, and group DML statements into transactions. The

SQL statements used to incorporate DDL, DML and transaction control

statements within the body of a procedural language program, are known as

Embedded SQL statements. The oracle corporation is the world‟s leading

supplier of software for information management and world‟s second largest

independent software company. Oracle is the top selling multi-user RDBMS.

Most commonly used data types of Oracle are: char, varchar or varchar2,

number, date, long, long raw/ raw.

***



7

Review Questions

______________________________________________________

1. What are various categories in which we can divide the SQL

statements?

2. What are different data types of Oracle?

***

Hands on Session

Q1. SQL statements are divided into following categories

(a) DDL & DML (c) TCL

(b) DCL (d) ALL

Q2 Embedded SQL statements include

(a) DEFINE & OPEN (c) EXECUTE

(b) DECLARE (d) ALL

Q3. Oracle Data types include

(a) Varchar2 (c) Long

(b) BLOB (d) ALL

Solution Keys

1 d, 2 d, 3 d

***


Parteek Bhatia ________________________________________________________________________

8

Chapter Objectives In this chapter you will learn

SQL*PLUS Interface

Invoking SQL*PLUS from command line

Difference between SQL*PLUS and iSQL*PLUS

_________________________________________________________________

2.1 SQL*PLUS Interface

Oracle provides an interactive SQL tool called SQL*PLUS, which allows the

users to enter SQL commands and pass them to oracle Engine for execution.

SQL*PLUS is a character based interactive tool that runs in a GUI environment.

It is loaded on the client machine. This is the first tool to be used by most

programmers when they place their first step into ORACLE world.

Now commonly user, uses interactive SQL*Plus known as iSQL*Plus

through the browser. iSQL*Plus is an interactive interface (i refers to

interactive), to interact with Oracle engine through browser as depicted in figure

02 INVOKING SQL*PLUS



9

Figure 2.1: Interaction with Oracle Server through SQL*PLUS and

iSQL*PLUS interface

In this interface user can execute both SQL and PL/SQL statements, that‟s why

it is known as SQL*PLUS (SQL+PL/SQL).

The actions need to be performed by user to invoke iSQL*PLUS has been

shown in figure 2.2.


Parteek Bhatia ________________________________________________________________________

10

Figure 2.2: Step 1- Selection of Oracle from list of programs



11

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