A "Database" refers to a set of related data and the way it is organized.

• Access to these data is usually provided by a "database management system" (DBMS) consisting of an integrated set of computer software that allows users to interact with one or more databases and provides access to all of the data contained in the database.

• The DBMS provides various functions that allow entry, storage and retrieval of large quantities of information and provides ways to manage how that information is organized.

• Consider an example ofsmall database which consists of a customer table as shown

and order table, as shown in

The customer table contains all the details of the customers whereas the order table contains the order details placed by the customers.

Advantages of DBMS

i. Redundancy can be reduced:

Database systems can eliminate data redundancy, since all applications share a common pool of data. Essential information such as customer name will appear just once in the database.

ii. Inconsistency can be avoided:

Since the same information can be present at multiple files in file systems, data needs to be updated at all the files whenever any changes in data occur. For example, a changed customer address may be reflected in personal information file, but not in savings account file.

iii. Reduced programming effort:

By providing access to a pool of shared data and by supporting powerful data manipulating languages, database systems eliminate a large amount initial and maintenance programming.

iv. Security can be enforced:

Not every user should be able to access all the data. For example, in a banking system, payroll personnel need only the information about various bank employees. They do not need access to customer accounts.

v. Integrity can be maintained:

Centralized control of the data helps in permitting the administrator to define integrity constraints to the data in the database.