Introduction

Introduction

• Dr. E. F. Codd proposed the relational model fordatabase systems in 1970.
• It is the basis for the relational databasemanagement system (RDBMS).
• The relational model consists of the following:
  • Collection of objects or relations
  • Set of operators to act on the relations
  • Data integrity for accuracy and consistency

A relational database is a collection of relations or two dimensional tables.

Data models

Entity Relationship Model

Create an entity relationship diagram frombusiness specifications or narratives:

Scenario:

• “. . . Assign one or more employees to adepartment . . .”
• “. . . Some nikovits.departments do not yet have assignedemployees . . .”

Entity Relationship Modeling Conventions

Relating Multiple Tables

• Each row of data in a table is uniquely identified bya primary key (PK).
• You can logically relate data from multiple tablesusing foreign keys (FK).

Relational Database Terminology

Relational Database Properties:

• Can be accessed and modified by executingstructured query language (SQL) statements
• Contains a collection of tables with no physicalpointers
• Uses a set of operators