Introduction to Databases

A database is a structured collection of related / structures data / information stored electronically in a computer system.

Data refers to raw, unprocessed facts and figures—like text, observations, numbers, or symbols—that by themselves hold no specific meaning.

In essence, data lacks context and purpose on its own. It’s quantified using bits and bytes, which are the smallest units of information in computing. Data can be stored but remains meaningless until it’s processed into something usable.

Data refers to known facts that can be recorded and that have implicit meaning—such as names, telephone numbers, and addresses.

Key Characteristics of a Database

A database has the following implicit properties:

• Represents a Miniworld (Universe of Discourse - UoD):
  A database represents some aspect of the real world. This real-world context is sometimes called the miniworld or universe of discourse. Any changes occurring in the miniworld are intended to be reflected in the database.

• Logical Coherence:
  A database is a logically coherent collection of data with inherent meaning. A random or unorganized collection of data is not considered a database.

• Purpose-Driven Design:
  A database is designed, built, and populated with data for a specific purpose. It serves an intended group of users and is built with predefined applications in mind.

A database has some source from which data is derived, some degree of interaction with events in the real world, and an audience that is actively interested in its contents.

Database Management System (DBMS)

A Database Management System (DBMS) is a computerized software system that enables users to create, define, construct, manipulate, and share databases.

A database management system (DBMS) is a collection of interrelated data and a set of programs to access those data. The collection of data, usually referred to as the database, contains information relevant to an enterprise. The primary goal of a DBMS is to provide a way to store and retrieve database information that is both convenient and efficient.

A database is usually controlled by a database management system (DBMS). Together, the data and the DBMS, along with the applications that are associated with them, are referred to as a database system, often shortened to just database.

Purpose of Database Systems

Database systems were designed as a successor of the file processing system that had many disadvantages. These disadvantages were not there in the database systems and hence are the reasons for the development of the database systems. • Data redundancy and inconsistency • Difficulty in accessing data • Data isolation • Integrity problems • Atomicity problems • Concurrent access anomalies • Security problems

Core Functions of a DBMS

1. Defining the Database:
   This includes specifying data types, structures, and constraints. The definition or descriptive information (metadata) is stored in a database catalog or data dictionary.

2. Constructing the Database:
   This involves storing the data on a storage medium managed by the DBMS.

3. Manipulating the Database:
   Operations include:

   • Querying to retrieve specific data.
   • Updating to reflect changes in the miniworld.
   • Generating reports or summaries based on the data.

4. Sharing the Database:
   Multiple users and applications can access the database concurrently in a controlled manner.

5. Protection and Maintenance:

   • System protection against hardware/software failures.

   • Security protection against unauthorized or malicious access.

   • Long-term maintenance, as databases often have life cycles spanning many years.

Interaction with the Database

Application programs interact with the database by sending queries and transactions to the DBMS.

• A query is a request to retrieve specific data.

• A transaction may involve both reading and writing data.

The DBMS processes these requests, ensuring data consistency, integrity, and security.

Database System

A database system consists of:

• The database itself.

• The DBMS software.

• Application programs and user interfaces.

Together, they support the creation, usage, and maintenance of databases.

Database Design Process

Designing a database, whether for a new application or an existing one, involves several stages:

1. Requirements Specification and Analysis:
   Collecting and documenting the data needs of users and applications.

2. Conceptual Design: Creating a high-level data model (e.g., Entity-Relationship model) that can be manipulated using design tools. This stage helps in maintaining and evolving the design.

3. Logical Design:
   Translating the conceptual model into a logical model supported by the DBMS (e.g., relational model).

4. Physical Design:
   Defining storage structures, indexing, access methods, and other physical considerations for efficient data access.

5. Implementation and Maintenance:
   The database is implemented, populated with real data, and maintained over time to reflect ongoing changes in the miniworld.