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What Is a Relational Database?

A relational database stores all sorts of information in an organized way.
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  • Originally Written By: K. Powell
  • Revised By: Bott
  • Edited By: L. S. Wynn
  • Last Modified Date: 15 June 2014
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A relational database consists of a collection of tables that store particular sets of data. The invention of this database system has standardized the way that data is stored and processed. The concept of a relational database derives from the principles of relational algebra, realized as a whole by the father of relational databases, E. F. Codd. Most of the database systems in use today are based on the relational system; however, relational databases are built-in to software that people and companies purchase, so the database is generally invisible to the general public.

The history of the relational database began with Codd's 1970 paper, A Relational Model of Data for Large Shared Data Banks. This theory established that data should be independent of any hardware or storage system, and provided for automatic navigation between the data elements. In practice, this meant that data should be stored in tables and that relationships would exist between the different data sets, or tables.

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Database Content

The relation, which is a two-dimensional table, is the primary unit of storage in a relational database. A relational database can contain one or more of these tables, with each table consisting of a unique set of rows and columns. A single record is stored in a table as a row, also known as a tuple, while attributes of the data are defined in columns, or fields, in the table. The characteristics of the data, or the column, relates one record to another. Each column has a unique name and the content within it must be of the same type.

Cross-referencing Tables

Tables can be related to each other in a variety of ways. Functional dependencies are formed when an attribute of one table relates to attributes of other tables. The simplest relationship is the one-to-one relationship, in which one record in a table is related to another record in a separate table. A one-to-many relationship is one in which one record in a table is related to multiple records in another table. A many-to-one relationship defines the reverse situation; more than one record in a single table relates to only one record in another table. Finally, in a many-to-many relationship, more than one record in a table relates to more than one record in another table.

Differentiating Data

When referring to a relational database, a key is an entity in a table that distinguishes one row of data from another. The key may be a single column, or it may consist of a group of columns that uniquely identifies a record. Tables can contain primary keys as well as foreign keys. Primary keys serve to differentiate records from one another; they can be an individual attribute or a combination of attributes. Foreign keys relate tables in the database to one another, and generally define the parent-to-child relationships between tables. Also, a foreign key in one table may be a primary key in another.

Organizing Data

The data that is stored in tables is organized in a logical manner based on a particular purpose to help minimize duplication, reduce data anomalies, and reinforce data integrity. The process by which data is logically organized is called normalization; it not only simplifies the way data is defined, but it also regulates its structure. There are five forms in the normalization process, with each form meeting a more demanding condition. The first normal form, 1NF, meets the minimal requirements for normality and has the least data integrity, while the fifth normal form, or 5NF, structures the data with the least anomalies and the best integrity.

Stored data is manipulated using a programming language called Structured Query Language, or SQL. Many varieties of SQL exist, but most are based on set theory relational operators such as and, or, not, and in, all of which are used to perform operations on the data. The operations that can be used in relational databases include insert, select, update, and delete privileges.

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In the early 2010s, the relational database management system (RDBMS), is the most commonly used database format; it is often used by businesses and corporations to help update and administer relational databases. Historically, there have been three leading RDBMS companies: Oracle®, who created the first commercial relational database in 1979; IBM®, who followed suit in 1982 with the SQL Data System, later renamed DB2®; and Microsoft®, who joined in with SQL Server® 4.2 in 1992. Other companies also offer RDBMS products, most of which can be purchased from the company's website or in retail stores that sale computer software, and prices vary depending on the company.

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Discuss this Article

anon946744
Post 20

Can someone kindly elaborate on the structure of RDBMS, like where is the data stored, what hardware is used and what software is used, how can we set up a RDBMS on our own?

anon355962
Post 19

What is database mining?

anon240169
Post 15

The relational database in not called relational because there are relations between the tables. The name relational comes from relational theory which defines a relation as a set of tuples that have the same attributes. In a relational database a row is equivalent to a tuple and a table represents a relation.

anon101458
Post 12

why is a relational database called so?

Answer: In a database, one table has a relation to another table, thus forming a relationship between two tables.

This type of relation between tables in database is known as a relational database.

The concept was developed by Dr. Codd.

So, to do all these there is a software called DBMS and the management system is RDBMS. RDBMS products are DB2, oracle, etc.

anon80528
Post 11

What is the distinguishing characteristic of a relational database?

anon80478
Post 10

i think this article has helped me a lot as part of my assignment. thank you very much.

anon66186
Post 7

what is advanced database application?

anon64557
Post 6

this is a very helpful source to my work. sincerely ATIF

anon64107
Post 5

it was helpful.

anon19326
Post 2

why is a relational database called so?

anon18104
Post 1

i think that this article was very helpful and i will continue to use your website in future assignments.

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