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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.
                    Clickipedia

                     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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