Module II

Data Resource Management

What is a 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 joining, Salary.

What is a Database Management System?DBMS is a software system that allows its users to access the data contained in the database, in the form that they want.

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:

Salary Management System andTicket reservation system

Functions of DBMS

Benefits of a DBMS?

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

Traditional File System:Information typically stored using file-processing system

File processing is the process of creating, storing and accessing content of files

Disadvantages of the file-processing system:

1. Data redundancy – Same data may appear in several files2. Data inconsistency – Changes in data may not reflect in

all files3. Difficulty in data access 4. Data integrity – Database inaccurate and consistent5. Data security – User level security

DBMS example

In a Telephone System Manufacturing company with more than 2,500 employees , if the Management needs a report like:

List of employees getting a salary of more than 10,000?

SELECT * FROM Employee WHERE salary > 10,000

The above oracle or SQL command lists all records which have a salary more than 10,000

If it is a small company with 12 employees

Types of DBMS

Types of Databases

Hierarchical databaseNetwork databaseRelational databaseObject-oriented database

HIERARCHICAL DATABASEA DBMS is said to be hierarchical if the

relationships among data in the database are established in such a way that one data item is present as the subordinate of another one. 

Here subordinate means that items have 'parent-child' relationships among them.

NETWORK DATABASE A DBMS is said to be a Network DBMS if the

relationships among data in the database are of type many-to-many.

The structure of a network database is extremely complicated because of these many-to-many relationships in which one record can be used as a key of the entire database.

RELATIONAL DATABASE A relational database is a database that stores

 information about both the data and how it is related. "In relational structuring, all data and relationships are

represented in flat, two-dimensional table called a relation."

A number of RDBMSs are available, some popular examples are Oracle, Sybase, Ingress,Informix, Microsoft SQL Server, and Microsoft Access.

OBJECT-ORIENTED DATABASE Object-oriented databases use small, reusable chunks of

software called objects. Each object consists of two elements:

1) a piece of data (e.g., sound, video, text, or graphics), and

2) the instructions, or software programs called methods, for what to do with the data.