The document discusses database management systems (DBMS) and their advantages over traditional file-based data storage. It notes that a DBMS provides a centralized, organized collection of data that can be efficiently accessed and securely maintained. It also describes the three-level architecture of a DBMS, including the external, conceptual, and internal levels, and explains how this architecture provides logical and physical data independence. Finally, it briefly outlines some common database languages like DDL for defining schemas and DML for manipulating data.

1. Subject Name Code Credit Hours
FUNDAMENTAL COMPUTER PRINCIPLE & PROGRAMMING
DBMS

2. Subject Name Code Credit Hours
FUNDAMENTAL COMPUTER PRINCIPLE & PROGRAMMING
Database Management System
(DBMS)
• Collection of interrelated data
• Set of programs to access the data
• DBMS contains information about a particular enterprise
• DBMS provides an environment that is both convenient and
efficient to use.
• Database Applications:
– Banking: all transactions
– Airlines: reservations, schedules
– Universities: registration, grades
– Sales: customers, products, purchases
– Manufacturing: production, inventory, orders, supply chain
– Human resources: employee records, salaries, tax deductions
• Databases touch all aspects of our lives
D.Balaganesh LINCOLN UNIVERSITY COLLGE 2

3. Subject Name Code Credit Hours
FUNDAMENTAL COMPUTER PRINCIPLE & PROGRAMMING
Purpose of Database System• In the early days, database applications were
built on top of file systems
• Drawbacks of using file systems to store data:
– Data redundancy and inconsistency
• Multiple file formats, duplication of information in
different files
– Difficulty in accessing data
• Need to write a new program to carry out each new
task
– Data isolation — multiple files and formats
– Integrity problems
• Integrity constraints (e.g. account balance > 0)
become part of program code
• Hard to add new constraints or change existing ones
D.Balaganesh LINCOLN UNIVERSITY COLLGE 3

4. Subject Name Code Credit Hours
FUNDAMENTAL COMPUTER PRINCIPLE & PROGRAMMING
Purpose of Database Systems (Cont.)• Drawbacks of using file systems (cont.)
– Atomicity of updates
• Failures may leave database in an inconsistent state with partial
updates carried out
• E.g. transfer of funds from one account to another should either
complete or not happen at all
– Concurrent access by multiple users
• Concurrent accessed needed for performance
• Uncontrolled concurrent accesses can lead to inconsistencies
– E.g. two people reading a balance and updating it at the same time
– Security problems
• Database systems offer solutions to all the above
problems
D.Balaganesh LINCOLN UNIVERSITY COLLGE 4

5. Subject Name Code Credit Hours
FUNDAMENTAL COMPUTER PRINCIPLE & PROGRAMMING
Three-Level Architecture
5© Pearson Education Limited 1995, 2005

6. Subject Name Code Credit Hours
FUNDAMENTAL COMPUTER PRINCIPLE & PROGRAMMING
Three-Level Architecture
• External Level
– Users’ view of the database.
– Describes that part of database that is relevant
to a particular user.
• Conceptual Level
– Community view of the database.
– Describes what data is stored in database and
relationships among the data.
6

7. Subject Name Code Credit Hours
FUNDAMENTAL COMPUTER PRINCIPLE & PROGRAMMING
Three-Level Architecture
• Internal Level
– Physical representation of the database on
the computer.
– Describes how the data is stored in the
database.
7

8. Subject Name Code Credit Hours
FUNDAMENTAL COMPUTER PRINCIPLE & PROGRAMMING
Data Independence
• Logical Data Independence
– Refers to immunity of external schemas to
changes in conceptual schema.
– Conceptual schema changes (e.g.
addition/removal of entities).
– Should not require changes to external
schema or rewrites of application programs.
8

9. Subject Name Code Credit Hours
FUNDAMENTAL COMPUTER PRINCIPLE & PROGRAMMING
Data Independence
• Physical Data Independence
– Refers to immunity of conceptual schema to
changes in the internal schema.
– Internal schema changes (e.g. using different
file organizations, storage structures/devices).
– Should not require change to conceptual or
external schemas.
9

10. Subject Name Code Credit Hours
FUNDAMENTAL COMPUTER PRINCIPLE & PROGRAMMING
Data Independence and the Three-
Level Architecture
10© Pearson Education Limited 1995, 2005

11. Subject Name Code Credit Hours
FUNDAMENTAL COMPUTER PRINCIPLE & PROGRAMMING
Database Languages
• Data Definition Language (DDL)
– Allows the DBA or user to describe and
name entities, attributes, and relationships
required for the application
– plus any associated integrity and security
constraints.
11© Pearson Education Limited 1995, 2005

12. Subject Name Code Credit Hours
FUNDAMENTAL COMPUTER PRINCIPLE & PROGRAMMING
Database Languages
• Data Manipulation Language (DML)
– Provides basic data manipulation operations
on data held in the database.
• Procedural DML
– allows user to tell system exactly how to
manipulate data.
TCL transmission Control Language
12

13. Subject Name Code Credit Hours
FUNDAMENTAL COMPUTER PRINCIPLE & PROGRAMMING
Entity-Relationship Model
Example of schema in the entity-relationship model
D.Balaganesh LINCOLN UNIVERSITY COLLGE 13

14. Subject Name Code Credit Hours
FUNDAMENTAL COMPUTER PRINCIPLE & PROGRAMMING
• An ER model is an abstract way to describe a database.
Describing a database usually starts with a relational
database, which stores data in tables. Some of the data in
these tables point to data in other tables - for instance,
your entry in the database could point to several entries for
each of the phone numbers that are yours. The ER model
would say that you are an entity, and each phone number is
an entity, and the relationship between you and the phone
numbers is 'has a phone number'. Diagrams created to
design these entities and relationships are called entity–
relationship diagrams or ER diagrams