Skip to main content

Database Management System

Image


 Database oriented approach of Organising data provides a set of programs to facilitate users to organise, create, delete, update and manipulate data in a database. All these programs together form a Database management system ( DBMS). Features found commonly in database management system are described below :


Database models:

We saw that database integrates together multiple related files. A database model defines the manner in which a database links it's various data elements tougher. Four database models used commonly are, hierarchical, network, relational, and object oriented. Also known as database structure techniques, they are described below.

 

1. Hierarchical Database:

A hierarchical database links it's data elements as an inverted tree structure ( root at the top with branches formed below). Below the single root database element are subordinate elements, each of which, in turn has its own subordinate elements and so on, the can grow to multiple levels. Database elements of a hierarchical database have parent child relationship as in a family tree. A parent data element is one that has one or more subordinate data elements. Data elements that are below a parent data element are it's children data elements. There may be many children data elements under each parent element, but there can be only one parent element for any child element. Note that the branches of a tree structure are not connected.

Several database applications use hierarchical database because they can neatly organise their data elements as a hierarchical tree structure. However, the main limitations of hierarchical database  is that it does not support flexible data access. In a hierarchical database, applications can access it's data elements only by  following paths formed by branches of the tree structure. Hence, a database designer designing a hierarchical database must determine all types of relationships among the data elements and map them properly in a hierarchical tree structure while designing the database.

2. Network Database: 

A network Database is an extension of hierarchical database. A network Database also organises it's data elements I such a manner that they have parent child relationship among them. Like I'm hierarchical database, a database designer designing a network Database must determine all types of relationships among data elements while designing the database. In a network Database, however, a child database element can have more than one parent element or no parent element at all. Moreover in this type of Database, database management system permits extraction of needed information by beginning form any data element in database structure. Instead of starting form root data element.


3. Relational Database:

A relational database organises it's data elements as multiple tables with rows and columns. It stores each table as a separate file. Each table column represents a data field, and each raw represents a data record (also known a as tuple). A common field links data in one table or file to another table.

Relational database model provides greater flexibility of data organisation and future enhancement in database as compares to hierarchical and network Database models. Many applications can organise their data elements in a relational database in a manner that is identical to real life relationships between data elements. Hence, users often find relational database model to be closer to their intuitive model of real life situations, making making this model easier to use and understand. Moreover for adding new data to an existing relational database, there is no need to redesign the database afresh. Rather, user can add to the database new tables containing new data and can then link this tables to existing tables by common key fields. Users can also recognise data elements, when necessary, to create new table by selecting certain rows or specific columns from other tables or by joining columns and rows form two separate tables. 


4. Object Oriented Database:

Hierarchical, relational, and network data models are suitable for conventional business data processing applications, such as inventory control, payroll, accounts, employee information systems, etc. An application designers have found them unsuitable for a variety of other types of applications because of several serious shortcomings in them. This applications include computer-aided design( CAD), computer-aided engineering (CAE), computer-aided manufacturing (CAM), computer-aided software engineering (CASE), expert systems and multimedia systems. 

Object Oriented Database model overcomes this shortcomings of conventional database models. An object oriented database is a collection of objects whose behaviour, state, and relationships are in accordance with object oriented concepts ( such as abject, class, class hierarchy, etc.). An object oriented database management system allows definition and manipulation of an abject oriented database.

 




Labels:

Comments

Post a Comment

Popular posts from this blog

Word-processing Package

The term word processing describes use of hardware and software to create, edit, view, format, store, retrieve and print documents (written materials such as letters, reports, books, etc.). A word processing package enables us to do all these on computer system. Commonly supported features: Today's word processing packages normally support the features described below: 1. Entering Text : This feature allows a user to enter text with computer's keyboard. Every character typed on keyboard is displayed immediately on computer's screen. Word wrap feature of word processing software determines when current line is full, and it automatically moves the text that follows to the next line. Hence, only time the user has to press Enter key is at the end of the paragraph. This feature is very useful to those having fast typing speed because they can enter text at their speed, without the need to keep track of where to end a line. 2. Editing Text : This feature allows a user to make cha...
Post a Comment
Read more

Computer Languages - introduction

  This chapter continues with the discussion of development of computer programs. Once a programmer has finished planning of a computer program, he/she is now ready to write the steps of the corresponding algorithm in a programming language.  Computer language or programming language is a language acceptable to a computer system, and the process of writing instructions in such a language is called programming or coding.   The goal of this post is to introduce some popular programming languages.  Analogy with natural languages:   Language is a mans of communication. We use a natural language such as English, to communicate our emotions and ideas to others. Similarly a programmer uses a computer language to instruct computer what he/she want to do.  All natural languages (English, French, German, etc.) use a standard set of words and symbols for communication. Everyone uses that language understands these words and symbols. The set of words allowed in a ...
Post a Comment
Read more

Central Processing Unit

  Central Processing Unit (CPU) A Central Processing Unit is also called a processor, central processor, or microprocessor. It carries out all the important functions of a computer. It receives instructions from both the hardware and active software and produces output accordingly. It stores all important programs like operating systems and application software. CPU also helps Input and output devices to communicate with each other. Owing to these features of CPU, it is often referred to as the brain of the computer. Central Processing Unit CPU is installed or inserted into a CPU socket located on the motherboard. Furthermore, it is provided with a heat sink to absorb and dissipate heat to keep the CPU cool and functioning smoothly. Generally, a CPU has three components: 1. Control Unit 2. Arithmetic Logic Unit 3. Memory or Storage Unit 1. Control Unit : It is the circuitry in the control unit, which makes use of electrical signals to instruct the computer system for executing alre...
Post a Comment
Read more

Introduction to Computer

  The word "computer" comes from the word "compute", which means "to calculate". Hence, people usually consider a computer to be a calculating device that can perform arithmetic operations at high speed.  The straightforward meaning of a computer is a machine that can calculate. However, modern computers are not just a calculating device anymore. They can perform a variety of tasks. In simple terms, a computer is a programmable electronic machine used to store, retrieve, and process data. According to the definition, " A computer is a programmable electronic device that takes data, perform instructed arithmetic and logical operations, and gives the output." Whatever is given to the computer as input is called 'data', while the output received after processing is called 'information'. Although the original objective of inventing a computer was to create a fast calculating device, we name define a computer as a device that operates...
Post a Comment
Read more

Computer system architecture

  Computer Architecture  A computer system is basically a machine that simplifies complicated tasks. It should maximize performance and reduce costs as well as power consumption.The different components in the Computer System Architecture are Input Unit, Output Unit, Storage Unit, Arithmetic Logic Unit, Control Unit etc. A diagram that shows the flow of data between these units is as follows − The input data travels from input unit to ALU. Similarly, the computed data travels from ALU to output unit. The data constantly moves from storage unit to ALU and back again. This is because stored data is computed on before being stored again. The control unit controls all the other units as well as their data. Details about all the computer units are − Input Unit The input unit provides data to the computer system from the outside. So, basically it links the external environment with the computer. It takes data from the input devices, converts it into machine language and then loads ...
Post a Comment
Read more