Introduction to Relational Database Management System (RDBMS) and Relational Data Model, Slides of Introduction to Database Management Systems

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Database

Management

System

Lecture - 14

Logical Database

Design

Two Major Strengths

Simplicity

Strong Mathematical Foundation

Relational Data Model

Presented by E. F. Codd in 1970, then of IBM

Before Relational Data Model, two older data models were in use; Hierarchical, Network

Basic of RDM

RDM used mainly for external, conceptual, and to some extent physical schema Separation of conceptual and physical levels makes manipulation much easier, contrary to previous data models

Basic of RDM

RDM used for external, conceptual, and to some extent physical schema The basic structure is relation Both entities and relationships are modeled using tables/relations

Basics of RDM

Columns represent attributes and rows represent records

Rows, records and tuples all these terms are used interchangeably

Basic Properties of a Table

1. Each cell of a table contains atomic/single value
2. Each column has a distinct name; the name of the attribute it represents

Basic Properties of a Table

5. The order of the rows is immaterial
6. Each row/tuple/record is distinct, no two rows can be same

A table

stID stName clName doB sex S001 M. Suhail MCS 12/6/84 M S002 M. Shahid BCS 3/9/86 M S003 Naila S. MCS 7/8/85 F S004 Rubab A. MBA 23/4/86 F S005 Ehsan M. BBA 22/7/88 M

Mathematical Relations Consider two sets  A = {x, y} B = {2, 4, 6}  Cartesian product of these sets  A X B= {(x,2), (x,4), (x,6), (y,2), (y,4), (y,6)}

Mathematical Relations

A relation is some subset of this Cartesian product, For example,  R1= {(x,2), (y,2),(x,6),(x,4)}  R2 = {(x,4), (y,6), (y,4)}

Database Relations

Thinking in some real

world scenario

 Name = {Ali, Sana, Ahmed, Sara}  Age = {15,16,17,18,…….,25}

Database Relations

Cartesian product of Name & Age

Name X Age= {(Ali,15), (Sana,15), (Ahmed,15), (Sara,15), …., (Ahmed,25), (Sara,25)}

CLASS = {(Ali, 18), (Sana, 17), (Ali, 20), (Ahmed, 19)} Docsity.com