Click here for audio-text lecture and feed it to the speech agent

In the beginning

There was the record

Record is a collection of fields
File is a collection of records
Stored record is also called physical record
Logical record, in non-database systems, is identical to stored record

Example of Employee record: NAME, ADDRESS, DEPARTMENT, SALARY, ..

Evolution of Database Systems

1. Application program + File
2. Application program + File Manager + File
3. Application programs + File Manager + Files
4. Application programs + DBMS + Database

What is a Database

A database consists of some collection of persistent data that is used by the application systems of some enterprise

Persistent Data Includes

Operational data
Decision support data

Why Database?

Data sharing

compactness
speed
shared programs
currency
integrity
security

Data Independence

Freed from storage structure
Logical records can be considered without regard to physical records

Elements of a Database System

Integrated and shared data
Hardware

Software

Users

Database administrator

The Key Personnel for DBMS

Data Administrator DA
Database Administrator DBA

Evolution of Database Systems

1. Hierarchical database structure
2. Network database structure
3. Relational database structure
4. Object-oriented database structure

Key Concepts of Database Structure

Entities
Relationships

An Entitly-Relational Diagram

The Relational Approach

Data is perceived as tables
operators
mathematical foundation

Given table:        Cellar   WINE              YEAR       BOTTLES
                             Chardonnay          87             4
                             Fume Blanc          87             2
                             Pinot Noir          82             3
                             Zinfandel           84             9


Operators:

Projection:         Cellar   WINE           BOTTLES
                             Chardonnay           4
                             Fume Blanc           2
                             Pinot Noir           3
                             Zinfandel            9


Selection:          Cellar   WINE              YEAR       BOTTLES
                             Chardonnay          87             4
                             Fume Blanc          87             2