CREATE OWN LIBRARY

Relational Model

Introduction to Relational Model

After ER diagram (Conceptual level), we are discussing the representation level where we will discuss the Relational Model. 

At the representation level, we can choose one of the existing models and according to models we assume that our data is model in this way. So, depending on the type of database we are selecting our software (DBMS). 

Every DBMS does not access all types of databases. So, we are selecting DBMS as per which type of data model we are choosing. As we know various companies provide various DBMS like Oracle, mySQL, SQL server, etc. 

The most popular representation model is the Relational model compare to other models like the Hierarchical database model, Network model, Object-oriented database model, object-relational model, etc.

Relational Model is popular because it is easy choosing various RDBMSs. Most of the company who provides RDBMSs maintains a standard of the relational model and they all use SQL. 

Now what a procedure to design a database:

Firstly we complete the E-R diagram, then we will convert it to the corresponding relational model, and finally the database or physical model. 

After that, we install standard RDBMS and we use SQL which is the combination of Relational Algebra (RA) and Relational Calculus (RC).

Terminology of Relational database

Table – relation

Row – tuple

Column –attribute

Sort of integer value Variable {set of values} – domain

Heading schema $\mathbf{R}\mathbf{(}{\mathbf{A}}_{\mathbf{1}}\mathbf{,}\mathbf{ }{\mathbf{A}}_{\mathbf{2}}\mathbf{,}\mathbf{ }{\mathbf{A}}_{\mathbf{3}}\mathbf{)}$- relation schema

Number of attributes – Degree of relation

Number of element present – relation state

Relation schema – Intension

Table – Extension

Same as relation state – current relation state

Relation (table) is basically same as set. So, as same as set no duplicate value allowed at relation.

And non – application attribute we can make null.