Relational Algebra and Relational Calculus


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 


Asked by:- IIShriyaII
0
: 2622 At:- 6/11/2018 8:16:33 PM
dbms calculus algebra







2 Answers
profileImage Answered by:- vikas_jk

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.

https://www.w3schools.in/dbms/relational-calculus/

https://www.tutorialspoint.com/dbms/relational_algebra.htm

http://www.cs.sfu.ca/CourseCentral/354/lxwu/notes/chapter4.pdf

https://www.go4expert.com/articles/relational-algebra-operations-sql-t21166/

https://techdifferences.com/difference-between-relational-algebra-and-relational-calculus.html

Practice questions

https://courses.cs.washington.edu/courses/cse544/99sp/homeworks/sample/sample.html

https://pdfrog.com/download/relational_algebra_questions_with_solutions.pdf

http://www.edugrabs.com/relational-calculus/

The above links should clear your concept of Relational Algebra and Relational Calculus

0
At:- 6/12/2018 6:52:21 AM


profileImage Answered by:- sdmishra
Relational Algebra came in 1970 and was given by Edgar F. Codd (Father of DBMS). It is also known as Procedural Query Language(PQL) in PQL, a programmer/user has to mention two things, “What to Do” and “How to Do”.

Suppose our data is stored in a database, then relational algebra is used to access the data from the database.

The First thing is we have to Access the data, this needs to be specified in the query as “What to Do”, but we have to also specify the method/procedure in the query that is “How to Do” or how to access the data from the database.
 

Types of Relational Operations
  • Basic Operations
  • Derived Operations
Refer to this article to learn more about Relational Algebra in DBMS

Relational Calculus

Before understanding Relational calculus in DBMS, we need to understand Procedural Language and Declarative Langauge.
  1. Procedural Language - Those Languages which clearly define how to get the required results from the Database are called Procedural Language. Relational algebra is a Procedural Language.
  2. Declarative Language - Those Language that only cares about What to get from the database without getting into how to get the results are called Declarative Language. Relational Calculus is a Declarative Language.
So Relational Calculus is a Declarative Language that uses Predicate Logic or First-Order Logic to determine the results from Database.

Types of Relational Calculus in DBMS
  • Tuple Relational Calculus (TRC)
  • Domain Relational Calculus (DRC)
Refer to this article to learn more about Relational Calculus in DBMS
0
At:- 3/24/2022 5:19:31 AM






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