Database Systems: Concepts, Design and Applications, 2nd Edition

CHAPTER4

Relational Algebra and Calculus

4.1 INTRODUCTION

The relational database model originated from the mathematical concept of a relation and set theory. As discussed in Chapter 2, Section 2.7.6, it was first proposed as an approach to data modelling by Dr. Edgar F. Codd of IBM Research in 1970 in his paper entitled “A Relational Model of Data for Large Shared Data Banks”. This paper marked the beginning of the field of relational database. The relational model uses the concept of a mathematical relation in the form of a table of values as its building block. The relational database became operational only in mid-1980s. Apart from the widespread success of the hierarchical and network database models in commercial data processing until early-1980s, ...