Chapter 1 (Databases & Database Users)

Database

A collection of related data

Example:

• Student records

• Bank accounts

• Hospital patients

Data:

Known facts that can be recorded and have implicit meanings

Mini-World

A part of the real world we are storing data about.

Example:

• University → students, courses, grades

• Hospital → patients, doctors, appointments

DBMS vs Database vs Database System

Term	Meaning
Database	The data itself
DBMS	Software that manages the data
Database System	DBMS + Database (+ applications sometimes)

What Does a DBMS Do?

Typical DBMS Functions

A DBMS can:

1. Define the database
   (data types, structure, constraints)

2. Store data

3. Retrieve data (queries, reports)

4. Update data (insert, delete, update)

5. Support many users at the same time

6. Keep data correct & consistent

A DBMS allows defining, storing, retrieving, updating, and managing data securely for multiple users.

Main Characteristics of the Database Approach ⭐⭐⭐

This is THE MOST IMPORTANT PART

Self-Describing Nature

• DBMS stores data + description of data

• Description = Metadata

📌 Metadata = data about data
(example: table name, column type)

Program–Data Independence

Programs are independent of how data is stored

Meaning:

• You can change data structure

• Without rewriting programs

Data Abstraction

• Users don’t see storage details

• They see a conceptual view

Think:

“I don’t care how it’s stored, I just query it.”

Multiple Views

• Different users see different views

• Each user sees only what they need

Data Sharing & Multi-User Transactions

• Many users access data at the same time

• DBMS ensures:

  • Correctness

  • Consistency

  • Recovery if failure happens

📌 Keyword: OLTP (Online Transaction Processing)

Example: UNIVERSITY Database

Entities:

• STUDENT

• COURSE

• SECTION

• INSTRUCTOR

• DEPARTMENT

Relationships:

• Students take sections

• Instructors teach sections

• Courses have prerequisites

• Students major in departments

👉 Exam questions often ask:

“Identify entities and relationships”

Types of Database Users

Actors on the Scene

People who use or manage databases

User	Role
DBA	Controls access, security
Database Designer	Designs structure
End Users	Query & use data
Application Programmers	Write programs

End Users Types

• Casual → occasional use

• Naïve / Parametric → predefined transactions (ATM, bank teller)

• Sophisticated → analysts, engineers

• Stand-alone → personal databases

Actors Behind the Scene

• DBMS developers

• Tool developers

• Operators & maintenance staff

Advantages of Using Databases

1. Reduced redundancy

2. Data sharing

3. Security

4. Backup & recovery

5. Multiple user interfaces

Don’t use DBMS if:

• System is small & simple

• Single user

• No future changes

DBMS may be infeasible:

• Embedded systems

• Very strict real-time requirements

If the question asks about:

• WHY DBMS? → advantages

• WHAT IS DBMS? → definition + functionality

• WHO USES DBMS? → user types

• HOW DBMS WORKS? → environment diagram