This summary of the database system refers to the book called 'Database Systems - A practical approach to design, implementation, and management (Publisher: Addison Wesley / Author: Thomas Connolly)'

Database : a collection of related data
DBMS (DataBase Management System) : the software that manages and controls access to the database

Example of database uses:
Purchases from the supermarket, purchases using your credit card, booking a holiday at the travel agent, using the local library, and etc.

Before DBMS became popular for data store, file-based system was used.

File-based system: A collection of application programs that perform services for the end-users such as the production of reports. Each program defines and manages its own data

Limitations of the File-based approach
1. Separation and isolation of data
2. Duplication of data
3. Data dependence
4. Incompatible file formats
5. Fixed queries/proliferation of application programs

Definition of Database

A shared collection of logically related data, and a description of this data, designed to meet the information needs of an organization.
( A Self-described collection of integrated records )

Description of data

System Catalog / data dictionary / metadata

Data abstraction of data

The approach taken with the database systems, where the definition of data is separated from the application programs, is similar to the approach taken in modern software development (Object oriented programming), where an internal definition of an object and a separate external definition are provided. This is known as Data Abstraction. The user of an object see only the external definition and are unaware of how the object is defined and how it functions.

Some terms

Entity: a distinct object in the organization that is to be represented in the database
Attribute: a property that describes some aspects of the object that we wish to record
Relationship: an association between entities

Definition of DBMS

A software system that enables users to define, create, maintain, and control access to the database

Database Application Programs

A computer program that interacts with the database by issuing an appropriate request (typically an SQL statement) to the DBMS

Views

- Views provide a level of security (Views can be set up to exclude certain data that some users should not see)
- Views provide a mechanism to customize the appearance of the database
- A view can present a consistent, unchanging picture of the structure of the database, even if the underlying database is changed

ROLES IN THE DATABASE ENVIRONMENT

DA (Data Administrator) : Responsible for the management of the data resource including database planning, development and maintenance of standards, policies and procedures, and conceptual/logical database design

DBA (Database Administrator) : Responsible for the physical realization of the database, including physical database design and implementation, security and integrity control, maintenance of the operating system, and ensuring satisfactory performance of the applications for users

Logical Database Designer : Responsible for identifying the data, the relationships between the data a, and the constraints of the data that is to be stored in the database

Physical Database Designer : Decides how the logical database design is to be physically realized

Application Developer : Develops an application program that provides required functionality for the end-users must be implemented

End-users: Naive users / Sophisticated users