Relational Algebra and Relational Calculus

Question

I am new to Database systems and I don't really have the best lecturer and we are learning about Relational algebra and relational calculus, not many videos or help online.  Please can someone assist me with this topic as i would like to get further knowledge

vikas_jk · Accepted Answer

Relational Algebra

A query language is a language in which user requests information from the database. it can be categorized as either procedural or nonprocedural. In a procedural language the user instructs the system to do a sequence of operations on database to compute the desired result. In nonprocedural language the user describes the desired information without giving a specific procedure for obtaining that information.

The relational algebra is a procedural query language. It consists of a set of operations that take one or two relations as input and produces a new relation as output.

Fundamental Operations

SELECT
PROJECT
UNION
SET DIFFERENCE
CARTESIAN PRODUCT
RENAME

Select and project operations are unary operation as they operate on a single relation.Union, set difference, Cartesian product and rename operations are binary operations as they operate on pairs of relations.

Relational Calculus

In contrast to Relational Algebra, Relational Calculus is a non-procedural query language, that is, it tells what to do but never explains how to do it.

Relational calculus exists in two forms -

Tuple Relational Calculus (TRC) :Filtering variable ranges over tuples

Domain Relational Calculus (DRC) : In DRC, the filtering variable uses the domain of attributes instead of entire tuple values.

As both of the above topics are quite big to cover here, I have just provided basic defination but here are some of the links which will help you to understand it more clearly.