1. Introduction to Databases
CHAPTER 1
Introduction to Databases
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2. 1.1 Introduction Basic terms: Database – A collection of related data
Database Management System (DBMS) – The software that manages and controls access to the database
Database Application – A program that interacts with the database at some point in its execution
Database System – A collection of application programs that interact with the database along with the DBMS and the database itself
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3. 1.1 Introduction Examples of Database Systems
Purchases from the supermarket
Purchases using your credit card
Booking a holiday at the travel agents
Using the local library
Renting a video
Using the Internet
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4. 1.1 Traditional File-Based Systems
It is the predecessor for database system
The good reasons for studying it:
Understanding the problems inherent in file- based systems may prevent us from repeating these problems in database system
If you wish to convert a file-based system to a database system, understanding how the file system works will be extremely useful
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5. 1.2 File Based Approach and Limitations of the File-based Approach
File-based system – A collection of application programs that perform services for the end-users, such as the production of reports. Each program defines and manages its own data.
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6. 1.2 File Based Approach and Limitations of the File-based Approach
Separation and isolation of data
Duplication of data
Data dependence
Incompatible file formats
Fixed queries/proliferation of application programs
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7. 1.3 Database Approach and The Database Management System (DBMS)
Database – Shared collection of logically related data (and a description of this data), designed to meet the information needs of an organization.
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8. 1.3 Database Approach and The Database Management System (DBMS)
Shared collection – can be used simultaneously by many departments and users.
Logically related - comprises the important objects and the relationships between these objects.
Description of the data – the system catalog (meta-data) provides description of data to enable data independence.
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9. 1.3 Database Approach and The Database Management System (DBMS)
Database Management System (DBMS) – A software system that enables users to define, create, and maintain the database and that provides controlled access to this database.
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10. 1.3 Database Approach and The Database Management System (DBMS)
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11. 1.4 Components of the DBMS environment
Hardware
Can range from a PC to a network of computers.
Software
DBMS, operating system, network software (if necessary) and also the application programs.
Data
Used by the organization and a description of this data called the schema.
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12. 1.4 Components of the DBMS environment
Procedures
The instructions and rules that govern the design and use of the database.
People
The people that involved with the system
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13. 1.5 Roles in the Database Environment
Data and Database Administrator
Database Designers
Application Developers
End-Users
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14. 1.6 Advantages and Disadvantages of DBMS
Control of data redundancy
Data consistency
Sharing of data
Improved data integrity
Improved maintenance through data independence.
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15. 1.6 Advantages and Disadvantages of DBMS
Complexity
Cost of DBMS
Cost of conversion
Performance
Higher impact of a failure
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