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Database Servers

A database is defined as an organised collection of data that can be visualised as a container of
information. It is a powerful computer or a software that quickly adds, accesses, modifies or delete
the information in a database.

WHAT IS A RELATIONAL DATABASE?

A relational database is a type of database that stores data in several tables. These tables may
interlinked to get a common piece of information. The software package that is used to handle
relational databases is known as the Relational Database Management System (RDBMS). Microsoft
Access, Microsoft SQL Server, Oracle, MySQL, IBM DB2, PostgreSQL, etc. are some of the most
commonly used relational database management systems.
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The relational database was proposed by Edgar F. Codd. He gave a set of thirteen rules (Codd’s
rules) to define a Relational Database Management System.

For example, assume that in an organisation, there are three different tables that contain information
about Employee, Salary and Attendance. The first table contains information of each employee like
Employee Code, Name, Address, Designation, etc. The second table contains Employee Code, Basic
Salary, PF, HRA, etc. Similarly, the third table contains information about monthly attendance of each
employee including the Employee Code.

To generate the Pay Slip of an employee, Employee Name and Address can be obtained from the
first table, Basic Pay and other allowances from the second table and Monthly Attendance from the
third table. This information is interrelated to each other by their Employee Code.

Key Components of a Relational Database

The key components of a relational database are as follows:

Fields

Age Name Address Designation Phone
22 Andy New Market Lane Accountant 9908457245

Table 50 James H.B. Road Clerk 9955256841
Records
27 Sandra New Fashion Street Cashier 9865457815

32 Sandy J.P. Market Administrator 9905412874

Tables: A table is a collection of logically related records. The multiple records of a database are
arranged together in a tabular structure to make a table. A table is made of rows and columns.
A column, in general, represents a field that contains information of a specific type, whereas a
row represents a record that contains information from the related fields. A row in a table is also
called a tuple. A column in a table is also called an attribute. The number of attributes in a table
is the degree of that table. The number of tuples in a table is the cardinality of that table.

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