Database normalization was first proposed by Dr. Edgar F Codd as an integral part of RDBMS in order to reduce data redundancy and improve data integrity. These rules are known as E F Codd Rules.

(i) Database is a repository collection of related data organized in a way that data can be easily accessed, managed and updated.
(ii) Database can be a soft ware or hardware based, with one sole purpose of storing data.

Database normalization was first proposed by Dr.Edgar F Codd as an integral part of RDBMS in order to reduce data redundancy and improve data integrity. These rules are known as E FCodd Rules.

(i) SQL server
(ii) Oracle
(iii) MySql
(iv) Maria DB
(v) SQLite.

(i) Foxpro
(ii) dbase

(i) Database Administrators(DBA)
(ii) Application or software developers
(iii) End User
(iv) Database designers

The Database Management System can be divided into five major components as follows:
(i) Hardware
(ii) Software
(iii) Data
(iv) Procedures / Methods
(v) Database Access Languages

Database Administrators:
Database Administrator or DBA is the one who manages the complete database management system. DBA takes care of the security of the DBMS, managing the license keys, managing user accounts and access etc.
Application Programmers or software Developers:
This user group is involved in developing and designing the parts of DBMS.
End User:
All modern applications, web or mobile, store user data. Applications are programmed in such a way that they collect user data and store the data on DBMS systems running on their server. End users are the one who store, retrieve, update and delete data.
Database designers:
Database designers are responsible for identifying the data to be stored in the database for choosing appropriate structures to represent and store the data.

Object model stores the data in the form of objects, attributes and methods, classes and inheritance. This model handles more complex applications, such as Geographic information System (GIS),sdentific experiments, engineering design and manufacturing. It is used in file Management System. It represents real world objects, attributes and behaviors. It provides a clear modular structure. It is easy to maintain and modify the existing code.

An example of the Object model is Shape, Circle, Rectangle and Triangle are all objects in this model
(i) Circle has the attribute radius.
(ii) Rectangle has the attributes length and breadth.
(iii) Triangle has the attributes base and height.
(iv) The objects Circle, Rectangle and. Triangle inherit from the object Shape

Database Administrator or DBA is the one who manages the complete database management system. DBA takes care of the security of the DBMS, managing the license keys, managing user accounts and access etc.

Select	Project
1. Symbol - σ	1. Symbol - π
2. Selecting a subset with tuples	2. Contains a vertical subset of relation.
3. Select filters out all tuples that don't satisfy the condition.	3. Projection eliminates all attributes of the input relation except in the projection list.

Basis of Comparison	DBMS	RDBMS
Expansion	Database Management System	Relational Database Management System
Data storage	Navigational model ie data by linked records	Relational model (in tables). ie data in tables as row and column
Data redundancy	Exhibit	Not Present
Normalization	Not performed	RDBMS uses normalization to reduce redundancy
Data access	Consumes more time	Faster, compared to DBMS.
Keys and indexes	Does not use.	used to establish relationship. Keys are used in RDBMS.
Transaction management	Inefficient, Error prone and insecure	Efficient and secure
Distributed Databases	Not supported	Supported by RDBMS.
Example	Dbase, FoxPro.	SQL server, Oracle, mysql, MariaDB, SQLite.

Types of a Data Model:
1. Hierarchical Model
2. Relational Model
3. Network Database Model
4. Entity Relationship Model
5. Object Model.
1. Hierarchical Model:
(i) Hierarchical model was developed by IBM as Information Management System. In Hierarchical model, data is represented as a simple tree like structure form.
(ii) This model represents a one-to-many relationship i.e., parent-child relationship. One child can have only one parent but one parent can have many children.
(iii) This model is mainly used in IBM Main Frame computers.

2. Rational Model:
(i) The Relational Database model was first proposed by E.F. Codd in 1970. Nowadays, it is the most widespread data model used for database applications around the world.
(ii) The basic structure of data in relational model is tables (relations). All the information's related to a particular type is stored in rows of that table.
(iii) Hence tables are also known as relations in a relational model. A relation key is an attribute which uniquely identifies a particular tuple (row in a relation (table)).

3. Network Model:
Network database model is an extended form of hierarchical data model. The difference between hierarchical and Network data model is:
(i) In hierarchical model, a child record has only one parent node,
(ii) In a Network model, a child may have many parent nodes. It represents the data in many-to-many relationships.
(iii) This model is easier and faster to access the data.

(iv) School represents the parent node
(v) Library, Office and Staff room is a child to school (parent node)
(vi) Student is a child to library, office and staff room (one to many relationship)
4. Entity Relationship Model:
(i) In this database model, relationship are created by dividing the object into entity and its characteristics into attributes.
(ii) It was developed by Chen in 1976. This model is useful in developing a conceptual design for the database. It is very simple and easy to design logical view of data. The developer can easily understand the system by looking at ER model constructed.
(iii) Rectangle represents the entities. E.g. Doctor and Patient.
(iv) Ellipse represents the attributes E.g. D-id, D-name, P-id, P-name. Attributes describes the characteristics and each entity becomes a major part of the data stored in the database. Diamond represents the relationship in ER diagrams e.g; Doctor diagnosis the Patient.

5. Object Model:
(i) Object model stores the data in the form of objects, attributes and methods, classes and Inheritance.
(ii) This model handles more complex applications, such as Geographic information System (GIS), scientific experiments, engineering design and manufacturing.
(iii) It is used in file Management System. It represents real world objects, attributes and behaviors. It provides a clear modular structure. It is easy to maintain and modify the existing code.

(iv) An example of the Object model is Shape, Circle, Rectangle and Triangle are all objects in this model.
(i) Circle has the attribute radius.
(ii) Rectangle has the attributes length and breadth.
(iii) Triangle has the attributes base and height.
(iv) The objects Circle, Rectangle and Triangle inherit from the object Shape.

(a) i and ii

(c) Network model represents the data in many to one relationships