The relational model

Up until 1970, data access was diverse in nature and management. No standard or common approaches were available, and the term used to refer to what we now understand as databases was data banks, but their structures were quite different.

Of course, there were other models, such as the hierarchical model and the network model, but their specifications were somewhat informal.

In 1969 and the following years, an engineer at IBM (E.F. Codd) started publishing a series of papers in which he established the foundations of what we now understand as the relational model; especially, his paper, The relational model for database management, is now considered the RM manifesto. In this model, all data is represented in terms of tuples, and these tuples are grouped into relations. As a result, a database organized in terms of the relational model is called a relational database.

Properties of relational tables

The following are the properties of relational tables:

• All data is offered...