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BIS315

Database Management Systems

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Chapter 1
Introduction to
Databases

Dr. Jihene Kaabi Harrath

University Of Bahrain

First Semester 2010-2011

1



A database is a collection of related data.

• A Database Management System (DBMS) is the software that

BIS315

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Database Management Systems

Introduction

manages and controls access to the database.
• A database application is simply a program that interacts with the database at some point in its execution.
• A database system is a collection of application programs that interact with the database along with the DBMS and the database itself.

Dr. Jihene Kaabi Harrath

University Of Bahrain

First Semester 2010-2011

2

• Some uses of database systems:
Purchases from the supermarket,

BIS315

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Database Management Systems

Introduction

Purchases using your credit card,
Booking a holiday at the travel agents,
Using the local library,
Taking out insurance,
Renting a video,
Using the Internet,
Studying at university.

Dr. Jihene Kaabi Harrath

University Of Bahrain

First Semester 2010-2011

3

• A File-Based system is a collection of application programs that perform services for the end-users such us the production of

BIS315

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Database Management Systems

File-Based Systems

reports. Each program defines and manages its own data.
• File-based systems were an early attempt to computerize the manual filing system that we are all familiar with.
• The manual filing system works well while the number of items to be stored is small.
• However, it breaks down when we have to cross-reference or process the information in the files.

Dr. Jihene Kaabi Harrath

University Of Bahrain

First Semester 2010-2011

4

1. Separation and isolation of data: when data is isolated in separate files, it is more difficult to access data that should be

BIS315

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Database Management Systems

Limitations of the File-Based Approach

available.
2. Duplication of data: due to the decentralized approach taken by each department, the file-based approach encouraged the
uncontrolled duplication of data that is undesirable for several reasons, including:
Duplication is wasteful. It costs time and money to enter the data more than once.
It takes up additional storage space.
Duplication can lead to loss of data integrity.

Dr. Jihene Kaabi Harrath

University Of Bahrain

First Semester 2010-2011

5

3. Data dependence: the physical structure and storage of the data files and records are defined in the application code

BIS315

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Database Management Systems

Limitations of the File-Based Approach

changes to an existing structure are difficult to make.
4. Incompatible file formats:

ex.

the

structure of

a

file

generated by a COBOL program may be different from the
structure of a file generated by a ‘C’ program

the direct

incompatibility of such files makes them difficult to process jointly. 5. Fixed queries: in some organizations, the type of query or report that could be produced was fixed. There was no facility for asking unplanned queries.

Dr. Jihene Kaabi Harrath

University Of Bahrain

First Semester 2010-2011

6



All the above mentioned limitations of the file-based approach can be attributed to two factors:

BIS315

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Database Management Systems

Limitations of the File-Based Approach

1. the definition of the data is embedded in the...
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