Relational Database Concept

Relational Model

The principles of the relational model were first outlined by Dr. E. F. Codd in a June 1970 paper called “A Relational Model of Data for Large Shared Data Banks.” In this paper, Dr. Codd proposed the relational model for database systems.

The more popular models used at that time were hierarchical and network, or even simple flat file data structures. Relational database management systems (RDBMS) soon became very popular, especially for their ease of use and flexibility in structure. In addition, a number of innovative vendors, such as Oracle, supplemented the RDBMS with a suite of powerful application development and user products, providing a total solution.

Components of the Relational Model

• Collections of objects or relations that store the data
• A set of operators that can act on the relations to produce other relations
• Data integrity for accuracy and consistency

Definition of a Relational Database

A relational database uses relations or two-dimensional tables to store information.
For example, you might want to store information about all the employees in your company. In a
relational database, you create several tables to store different pieces of information about your
employees, such as an employee table, a department table, and a salary table.

Data Models

Models are a cornerstone of design. Engineers build a model of a car to work out any details before putting it into production. In the same manner, system designers develop models to explore ideas and improve the understanding of the database design.

Purpose of Models

Models help communicate the concepts in people’s minds. They can be used to do the following:
• Communicate
• Categorize
• Describe
• Specify
• Investigate
• Evolve
• Analyze
• Imitate

The objective is to produce a model that fits a multitude of these uses, can be understood by an end user, and contains sufficient detail for a developer to build a database system.

Relational Database Properties

A relational database:
• Can be accessed and modified by executing structured query language (SQL) statements
• Contains a collection of tables with no physical pointers
• Uses a set of operators