DBMS Notes

Introduction to Relational Algebra

Relational Algebra is not actually implemented anywhere. It is collection of mathematical expressions. So it is a theoretical or logical model to access the database.

In simple words we can say, Relation Algebra provides the base to SQL and Non-SQL. SQL and Non-SQL are physically implemented. SQL database software’s are (MySQL, SQL Server, Oracle, Informix, IBM DB2 etc.)

This theoretical database model came in 1970.  This model was develop by EF CODE which is consider as the father of Database.

Relational Algebra is a procedural query language or formal query language.  In procedural query language every user has to mention two things to access data

  1. What to do?
  2. How to do?

Relational Algebra is just like C language where  we have to tell, what to do? And how to do? , before to access data.

Note: Concept of Relational Algebra and SQL is same but the SYNTAX is different. If we understand the operation of Relational Algebra then we easily move to SQL and Non-SQL.

So we learn Relational algebra before to learn SQL and Non-SQL.

Operators in Relational Algebra

Relational Algebra has three types of operators as in the following diagram

 

In upcoming lectures we will cover all operators one by one 

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