A Relational Database is an abstract concept that defines ways to store, manipulate and retrieve structured data solely in the form of data tables.
The term is applied to the data itself, when organized in this way, or Relational Database Management System (RDBMS) – a computer program that implements the abstraction.
Relational databases emerged in the mid -1970s. However, companies began to use them only a few years later in place of flat file, hierarchical databases and network.
In 1985, Edgar Frank Codd, creator of the relational model, published an article which defined rules for the Relational Database Management System (RDBMS), some of these rules include:
Fundamental Rule :
A relational DBMS must manage the data using only its relational capabilities
Rule of information :
All information should be represented in a unique way, as data in a table
Guaranteed access rule :
Any given atomic value can be reached logically using the name of the table, the primary key value of the row and the column name.
Systematic treatment of null values:
Null values (different from zero, the empty string, the string of characters in whites and other non-null values), there is no existing data to represent in a systematic way, independent of data type.
With the relational databases model, the place and the way data is stored are not relevant (unlike other models such as the hierarchical and network).
This has the considerable advantage that it is easier to understand and use for an occasional user of the database.
The information can be retrieved or stored by “consultations” that provide broad flexibility and power to manage information.
The most common language for building queries to relational databases is SQL, Structured Query Language, a standard implemented by the main database management systems or relational databases.
During design, a relational database undergoes a process which is known as a standardized database.
During the 80’s the emergence of dBASE was a revolution in programming languages and database management systems.