Saturday, July 30, 2016

Database Management System

A database is an organized collection of logical data. DBMS or Database Management System is the system software that stores and sustains the database. Database Management System is a window that allows users to interact with the database.

Major industries like Telecom, Hotel, Airlines, Textiles, Health, Education, Insurance uses some or the other DBMS software. There are wide varieties of DBMS software available in the market. Database systems like MS-SQL Server, DB2, SAP, CouchDB, PostgreSQL, SQLite, Sybase, RethinkDB, Berkeley, Redis, mongoDB, MySQL, Oracle, MS-Access are popular DBMS available in the market.

In the period of 1960s, Charles Bachman designed the first general purpose DBMS named as 'Integrated Data Source' which formed the basis of Network Data Model. He received ACM's Turing Award for his work in 1973.

In late 1960s, IBM developed Information Management System (IMS) DBMS for NASA's Apollo space program. This formed the basis of Hierarchical data model.

In 1970, Edgar Codd, at IBM, introduced Relational Data Model. The relational DBMS benefits and utilities were universally accepted by the industries and the corporate world for storing the data. Relational DBMS is more user-friendly and easy to use as compared to network and hierarchical data model.

Structured Query Language in DBMS
SQL is an ANSI and ISO standard language, developed to interact with the database. Earlier, SQL was popular as SEQUEL. SQL includes language elements like clauses, expressions, predicates, statements, and queries. SQL communicates with the database via DDL, DML, DCL, and TCL. The data structures and schemes are defined under DDL or Data Definition Language. DML or Data Manipulation Language includes insert, update, select and deletion of records. DCL or Data Control Language authorizes data access to users by Grant and Revoke statements. TCL or Transaction Control Language includes data transactions.

Elements Of DBMS
  1. Physical database
  2. Database engine
  3. Database scheme
  4. Schema objects
  5. Tables
  6. Fields
  7. Records
  8. Keys
  9. Relationships
  10. Data types
Advantages of DBMS
  1. Data security and consistency are very important when multiple users access the database simultaneously.
  2. Data retrieval is fast.
  3. Developing and maintaining DBMS is easier as compared to the file system.
  4. There is an inbuilt utility of backup and recovery when the system crashes.
Disadvantages of DBMS
  1. Complexity increases with increase in the size of data.
  2. Maintenance is expensive.