Relational Database

Objectives

In this section, you will learn to:

Define a Database Management System (DBMS)
Identify the components of a DBMS
Describe the need for a database system
Define the architecture of a DBMS in terms of:
External level
Conceptual level
Internal level
Identify the functional components of a DBMS
Identify the need for database planning
Identify the stages in the Database Development Life Cycle (DDLC)
Identify the effects of poor database planning and design

Introduction to Database
Management System

A database is a collection of records.
Database management systems are designed to maintain large volumes of data.
The main objectives of any DBMS are to:
Provide an efficient and convenient environment that is used to store data in and retrieve data from a database.
Manage information about users who interact with the DBMS and the activities that these users can perform on the data.

Users

There are three types of DBMS users:
Application Programmers: Application programmers write application programs that help an end user to use the database.
End Users: End users interact with a DBMS either by invoking an application program or by writing queries in a database query language.
Database Administrators (DBAs): Database Administrators (DBAs) coordinate the function of collecting information about the data to be stored, and designing and maintaining the database and its security.



Why use a Database Management
System?

The conventional approach to database processing has the following drawbacks:
Duplication of data
Inconsistent data
Some benefits of the database approach are:
Redundancy is reduced
Inconsistency is avoided
Data is shared
Standards are enforced
Security restrictions are applied
Integrity is maintained


Architecture of a Database
Management System

The architecture of a database management system can be broadly divided into three levels:
External level: It is also called the user view. This view describes only a part of the actual database.
Conceptual level: The conceptual level represents the entire database as a whole and is used by the DBA.
Internal level: This level deals with the physical storage of data and is the lowest level of the architecture.
Mapping determines the correspondence between one level and another.
There are two levels of mapping involved in this architecture. One is between the external and the conceptual levels, while the other is between the conceptual and the internal levels.



Functional Components of a Database
Management System

The functional components of a database management system are:
Database manager: The database manager is the central software component of a DBMS. It is responsible for converting user queries to appropriate system calls.
File manager: The file manager services all requests for data. It identifies the block containing the requested record.
Disk manager: The disk manager performs all the physical input and output.


Database Designing and Planning

Database planning is a strategic process of finding out the information needs of an organization for an extended period in the future.
The advantages of database planning are:
It gives a clear picture of the management’s current understanding of the information resource.
It finds and justifies resource requirements. This helps ensure the availability of resources.
It helps in effective resource management. This includes proper cooperation between divisions within the organization.
It helps specify action plans for achieving the set objectives.
It helps develop an appropriate database that meets the organization’s requirements.


Database Development Life Cycle

The DDLC consists of the following six stages:
Preliminary planning: At this stage, the organization obtains information about the applications being used.
Feasibility study: This stage involves determining technological, operational, and economic feasibility of a database.
Requirements definition: This stage involves determining the scope of the database, management and functional area information requirements, and hardware and software requirements.
Conceptual design: At this stage, you need to create the conceptual schema for the database.
Implementation: At this stage, you need to select a DBMS and purchase it. Then, you need to convert the detailed conceptual model to the implementation model of the DBMS.
Database evaluation and maintenance: This stage involves evaluating the performance of the implemented database.

Effects of Poor Database Planning and
Design

If you do not give ample amount of time and effort to database planning and design, the database can eventually fail.

Summary

In this lesson, you learned that:
A DBMS is a collection of interrelated data and a set of programs to access this data.
The main objectives of any DBMS are to:
Provide an efficient and convenient environment that is used to store data in and retrieve data from a database.
Manage information about users who interact with the DBMS and the activities that these users can perform on the data.
The users of a DBMS can be broadly classified into application programmers, end-users, and database administrators (DBA).
Summary (Contd..)

A DBMS provides the following benefits:
Reduced redundancy
Consistency
Data sharing
Standards enforcement
Security restrictions
Integrity
The database architecture consists of the external level, the conceptual level, and the internal level.
The functional components of a DBMS are:
Database manager
File manager
Disk manager


Summary (Contd..)

Database planning is a strategic process of finding out the information needs of an organization for an extended period in the future. It helps to design and implement databases.
The Database Development Life Cycle (DDLC) consists of the following six stages:
Preliminary planning
Feasibility study
Requirements definition
Conceptual design
Implementation
Database evaluation and maintenance
If you do not give ample amount of time and effort to database planning and design, the database can eventually fail.