As a collection of algebraic structures, relational algebra was developed at IBM by Edgar F. Codd. It is used to represent data stored in relational databases, as well as to define queries on that data. An instance of relational algebra may be described as a procedural query language that employs unary or binary operators to execute queries. Users of relational database systems must be able to query database instances using a query language. Relational algebra or relational calculus is used to query a relational database system. Recursive relational algebra is done on a relation, and intermediate outcomes are also considered relations. For Edgar F. Codd's relational paradigm, SQL was one of the first commercially available programming languages. Despite the fact that they are based on similar principles, their syntax differs. There are several advantages to relational algebra, including its closed nature, rigorous basis, and simplicity of semantics. SQL, on the other hand, is a subset of relational algebra with easy formatting capabilities, aggregate functions, and a complex semantics. Below is an example from the course readings that illustrate the difference in syntax:

SELECT DISTINCT dname
FROM department, course, empcourse, employee WHERE cname = `Further Accounting'

AND course.courseno = empcourse.courseno AND empcourse.empno = employee.empno AND employee.depno = department.depno;

The equivalent relational algebra is

PROJECTdname (department JOINdepno = depno ( PROJECTdepno (employee JOINempno = empno (

PROJECTempno (empcourse JOINcourseno = courseno ( PROJECTcourseno (SELECTcname = `Further Accounting' course)

pur-new-sol

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