Skip to main content

Introduction to Relational algebra & Relational calculus

 

Capgemini - Oracle training at  Chennai Freshers intake 2018



Introduction to Relational algebra & Relational calculus


In this guide, we will discuss what is Relational algebra and relational calculus and why we use these concepts. In the previous tutorials, we discussed the designing of database using Relational model, E-R diagram and normalization. Now that we have designed the database, we need to store and retrieve data from the database, for this purpose we need to understand the concept of Relational algebra and relational calculus.

Let’s start with the basics.

Query Language

In simple words, a Language which is used to store and retrieve data from database is known as query language. For example – SQL

There are two types of query language:
1.Procedural Query language
2.Non-procedural query language

Relational Algebra and Calculus - Query Language type

1. Procedural Query language:

In procedural query language, user instructs the system to perform a series of operations to produce the desired results. Here users tells what data to be retrieved from database and how to retrieve it.

For example – Let’s take a real world example to understand the procedural language, you are asking your younger brother to make a cup of tea, if you are just telling him to make a tea and not telling the process then it is a non-procedural language, however if you are telling the step by step process like switch on the stove, boil the water, add milk etc. then it is a procedural language.

2. Non-procedural query language:

In Non-procedural query language, user instructs the system to produce the desired result without telling the step by step process. Here users tells what data to be retrieved from database but doesn’t tell how to retrieve it.

Now let’s back to our main topic of relational algebra and relational calculus.

Relational Algebra:

Relational algebra is a conceptual procedural query language used on relational model.

Relational Calculus:

Relational calculus is a conceptual non-procedural query language used on relational model.

Note:
I have used word conceptual while describing relational algebra and relational calculus, because they are theoretical mathematical system or query language, they are not the practical implementation, SQL is a practical implementation of relational algebra and relational calculus.

Relational Algebra and Calculus Introduction

Relational Algebra, Calculus, RDBMS & SQL:

Relational algebra and calculus are the theoretical concepts used on relational model.

RDBMS is a practical implementation of relational model.

SQL is a practical implementation of relational algebra and calculus.

In the next tutorials we will cover the relational algebra and calculus in detail.

Comments

Post a Comment

Popular posts from this blog

Oracle Merge Statement Delta Detection

The MERGE Syntax by Ajay Nerumati Delta Detection in Oracle SQL Posted on  8. October 2016 Delta detection is a common task in every Data Warehouse. It compares new data from a source system with the last versions in the Data Warehouse to find out whether a new version has to be created. There are several ways to implement this in Oracle. Your source system delivers a full extraction every night, and you have to load only the changed rows into your Core Data Warehouse? You receive incremental loads from another source system every few minutes, but only a few columns are loaded into the Data Warehouse. In all these situations, you need a delta detection mechanism to identify the rows that have to be inserted or updated in your Data Warehouse tables. In this blog post, I want to show different methods in Oracle SQL that provide the subset of rows of a source table that were changed since the last load. All these methods are set-based, i.e. they can be executed in one SQL sta...
199 comments
Read more

FOREIGN KEY

Pre-requisits : General understanding of integrity constraints. Constrains are used to prevent invalid data into the table. Integrity constrains are business rules enforced on the data in a table. The enforced rules trigger whenever a row is inserted, updated, or deleted from that table and prevent data that does not meet the set rules. FOREIGN KEY :  Establishes and enforces a relationship between two tables or to the same table itself. The foreign key or referential integrity constraint, designates a column or combination of columns as a foreign key and establishes a relationship between a primary key or a unique key in the same table or a different table.  In the example below   Emp_child  table's deptno   has been defined as the foreign key ; it references the deptno column of the Dept_parent table. Implementation: Step 1 Create parent table DEPT_PARENT as follows: Create table DEPT_PARENT ( Deptno n...
79 comments
Read more

RDBMS MINI PROJECT

  Capgemini class room training.   RDBMS MINI PROJECT ( SPRINT ) LIBRARY MANAGEMENT SYSTEM   Table of Contents Serial No. Topic Name Content Page No. 1.   Introduction 1.1 Setup checklist for mini project 3     1.2 Instructions 3 2.   Problem statement   2.1 Objective 4     2.2 Abstract of the project 4     2.3 Functional components of the project 4     2.4 Technology used 5 3.   Implementation in RDBMS LOT 3.1 Guidelines on the functionality to be built 6 4.   Evaluation 4.1 Evaluation 7   ...
1 comment
Read more