A Database Management System is said to be Relational DBMS if it works based on Relational model. This was introduced by E.F.Codd in 1969.
A relational database is a collection of data organized and described in terms of related tables from which data can be accessed easily. A relational database is created using the relational model.
In the relational model entire data is represented in terms of rows(tuples) which are grouped into relations. A relation among the data is usually described as a table, which is organized into rows and columns. While discussing about RDBMS, some folks might use some terminology like Tuple and Attribute. Actually Tuple means a row and Attribute means a column. As of now almost all the popular databases are based on Relational model only. Most of the Relational Database Management Systems use the Structured Query Language(SQL) to access the data from database. Since Relational databases are easier to understand, It replaced hierarchical databases and network databases even though they are less efficient.
The most popular RDBMS are Oracle, SQL Server, DB2, Sybase etc…
The vendors of the five leading RDBMS are,
I do not know why, if someone wants to give an example on database, 95% of the people choose Employee and Department tables. So let’s follow the same trend as everyone
In the above example, both the tables have a common column called DepartmentID. So we can say that, these two tables are related based on DepartmentID column.
By joining these two tables based on DepartmentID, we can retrieve the required data. We will discuss about joins in the upcoming tutorials.