What is Relational Database Management System ?

Introduction

 Relational Database Management System (RDBMS) is a database management system . Only  Relational databases are a database that stores data in a structured format.  

Rows and columns are used to store data in a relational database.  A relational database makes a specific value easy to locate and access.  

In a relational database, the values ​​of each table are related to each other.  RDBMS also provides a visual representation of the data.  It is very easy to store, update, search data in a relational database.  

All modern database management system is based on the relational database management system.




Relational Algebra in Relational Database Management System 

Relational Algebra is a group of operations that are used to manipulate data from relation to

Relational algebra is a procedural language in which an operator is used to perform queries and it is an intermediate language used in DBMS.

Relational Algebra has the following operators,

 1. Union(U)

 2. Difference(–)

 3. Selection (σ)

 4. Projection (∏)

 5. Cartesian Product(X)

 6. Intersection(∩)

 7. Rename(ρ)

 8. Join


Selection (σ) 

The sigma (σ) symbol denotes this.  Select operation is used to select a subset of the tuples according to the condition of a given selection.  

It is used as an expression to select tuples that satisfy the selection condition.


Difference (–) 

The difference operator is represented by the ( – ) symbol.  The result of the difference operation is Tuples, which are present in one relation but not in the other relation.


Projection (∏) 

Projection eliminates all features of the input relation but those mentioned in the projection list.  

The projection method defines a relation that has a vertical subset of relation.  

It helps to extract values ​​of specified attributes to eliminate duplicate values.


Union(U) 

Union Operation is represented by the (∪) symbol.  Union Operation has two input relations which are union compatible.  

The output relation of this operation contains those tuples (ROW) which are in Relation 1 and Relation 2.  

And those duplicate tuples are destroyed or eliminated.


Join 

This operator combines two relations into a new relation.

The join operators are of the following types,

  1. Theta(θ) Join

  2. Left Outer Join

  3. Right Outer Join

  4. Full Outer Join

  5. Natural Join ( )


Cartesian Product(X) 

This type of operation is helpful in joining columns from two relations.  

In general, a Cartesian product is never a meaningful operation when performed alone.  

However, it becomes worthwhile when it is followed by other tasks.


Intersection(∩) 

This operator is represented by the sign.  This operator is used to select common tuples from two relations.


Rename(ρ) 

Rename is a unary operation used to rename attributes of a relationship.


Benefits of Relational Databases

 Easy to understand and use: It is very easy to understand and use a relational database, because the structure of the relational database is very simple, due to which it is very easy to understand.  And it has columns and rows in its table, due to which it is very easy to use.  And to access it, you have to use SQL which is very easy.

 This reduces data redundancy: In a relational database management system, each table contains specific data and if you ever need it, you can easily access the data by linking different tables to it, and in this, you can easily access the data.  There is also no problem with duplicate data.

 Data is said to be secure: Data in a relational database is secure because the database administrator has all the access to it, but some users are also given some access to it by the administrator, due to which it remains very secure.

 It is flexible: Relational databases are very flexible, due to which we can create as many tables as we want in it, and can also increase their size and link it among themselves.

 Multi User: It means that more than one user can easily access it at the same time in relation database, and can also update the data.


Characteristics of Relational Databases

 In relational databases, all the data is stored in tables.

 In this, it is ensured that all the donors are stored in the form of rows and columns.

 The concept of the primary key is used for the unique identification of each row in the Relational Database.

 In this, you can extract data by joining two different tables together with the help of a foreign key.

 There is a validation rule in the Relational Database, due to which we can easily find out in which column, how many and which data has been entered.

 With the help of its normalization process, you can organize it without redundancy.

 You can simplify the speed of data retrieval by creating a Relational Database index.  Apart from this, with the help of its virtual table, we can simplify the queries.


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