Database Management System By Prakash Date: 13 Nov 2010
What is database? A set of related data is called database. For example: Student database that consists of the following fields, Enrollment number, Student name, Department, Year, Address. Employee database that consists of the following fields, Employee number, Employee name, Department, Address, Date of joint, Salary.
What is Database Management System? DBMS is a software system that allows user to access the data contained in the database. DBMS acts as an interface between the user and the database. The user requests the DBMS to perform various operations (insert, delete, update and retrieval) on the database. For example: Train ticket reservation system and Bus ticket reservation system
Easy to use – Adding, updating and deleting data in database
Centralized control of database – Share database to multiple user
Data Security – User based security to the database
Before the introduction of DBMS: Information typically stored using file-processing system File processing is the process of creating, storing and accessing content of files Disadvantages in file-processing system:
Data redundancy – Same data may appear in several files
Data inconsistency – Changes in data may not reflect in all files
Difficult in data access – To take reports very difficult
Data isolation – Data are stored in various files
Data integrity – Database accurate and consistent
Data security – User level security
Real time example In the Telephone System Manufacturing company with more than 2,500 employees working in that company. Management asking the report like: Who are all getting salary more than 10,000?
SELECT * FROM Employee WHERE salary > 10,000 The above oracle command lists all records which the salary more than 10,000 If it is small company with 12 employees