Introduction to Database Management System
Now these days companies, institutions, big offices organisations and malls all require large amount of data to be stored securely and accurately for various purpose. For this computer plays a vital role for help and processing a computer day-to-day activities. Almost every organisation feel to use powerful computers with very high disk storage capacity by which they can save a large amount of required data and information. This method is secure and easy rather than the manual method like telephone directory, dairy, file system, etc. The efficient use of data for planning, product control, marketing, payroll, accounting and other functions in an organisation have a great impact for its competitive edge.
Database Concepts
Basic concepts of Database
Several key concepts of database are listed below.
(a) Data:- The term data means groups of information that represents some fact or records.
(b) Information:- Information is the raw data that has been verified to be accurate and timely produced.
(c) Database:- Database is nothing but the collection of interrelated data which is to be stored in a conceptual manner. Some of the examples on database are like maintaining stock in a small shop, employee details of a big hospital, railway or air ticket reservation system, etc.
Database engineering
Database engineering is an architectural approach to planning, analyzing, designing, and implementing applications within an organisation. It aims to improve the management of resources including to support the achievement of business goal. Database engineering has many purposes, including organisational planning, business process, application development, information systems planning and systems re-engineering etc. Database engineering is a discipline involving conception, modelling, creation of a database, data analysis, database administration and database documentation in an organisation.
Use of Database
- To add new information
- To view or retrieve the stored information
- To modify or edit the existing information
- To remove or delete the unwanted information
- Arranging the information in a desired order.
Features of database
Main features of data stored in a database is
- It is well organized.
- It is related.
- It is accessible in different orders without any difficulties.
- It is stored only once.
DBMS
DBMS stands for database management system. It consists of software that organizes the storage of data in a database. A DBMS controls the creation, maintenance, and the use of the database storage structures of organisations and of their users. In large systems, a DBMS allows users and other software to store and retrieve data in a structured manner.
Features of DBMS
The features of Database Management System are as follows:-
- Data storage , retrieval, and update
- A user-accessible catalog
- Transaction support
- Concurrency control services
- Recovery services
- Authorizaion services
- Support for data communication integrity services
- Services to promote data independence
- Utility services
- Query processor
- Data manipulation language pre-processor
- Database manager
- Data definition language compiler
- File manager
- Catalog manager
Advantages of DBMS
- Data independence : It provides an abstract view of the data that hides the details data representation and storage.
- Efficient data access: This is the advantage where we use variety of techniques to store and retrieve data.
- Data Integrity and security: We can ensure data integrity if the data is always enforced through integrity constraint.
- Data Administration: Data administration deals with the modelling of the data and treats the data as an organisational resource.
- Concurrent access and crash recovery:It ensures concurrent access of the data in such a way that the data is being accessed by only one user a time and also protects the system from crashes.
- Reduced application development time : It supports all important functions that are common to many applications.
Disadvantages of DBMS
The disadvantages of DBMS are as follows
- Complexity
- Size
- Performance
- Higher impact of a failure
- Cost of DBMS
- Additional hardware costs
- Cost of Conversion
Data Definition language or Data Description Language (DDL)
Data Description Language (DDL) allows users to define the database, specify the data types, and data structures, and the constraints on the data to be stored in the database usually through data definition language. DDL translate the schema written in a source language into the object schema. It creates the logical and physical layout of the database.
- CREATE
- ALTER
- DROP
Data Manipulation Language
Data manipulation language (DML) allows users to insert, update, delete and retrieve data from the database. It provides general query facility through structured query language (SQL).
- SELECT
- INSERT
- UPDATE
- DELETE
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