Introduction
Relational Algebra is a family of algebra used for modelling the
data stored in relational database, and defining queries on it.
Analogy between Relational Algebra and Arithmetic:
SQL is based on concepts of Relational Algebra.
Arithmetic is the elementary branch of mathematics that deals with study of numbers and properties of operations on them, like addition, subtraction, multiplication, and division.
In Relational Algebra the analogy of numbers are relations and its own set of operations to manipulate with relations, like select, project, join and other.