What are the different data models in the database management system?

The basic structure or design of the database is the data model. A data model is a

collection of conceptual tools for describing data, data relationships, data semantics, and

consistency constraints. Some data models are given below:

Entity-Relationship Model:

Entity-relationship (E-R) model is a high level data model based on a perception of a

real world that consists of collection of basic objects, called entities, and of relationships among

these entities. An entity is a thing or object in the real world that is distinguishable from other

objects. Entities are described in a database by a set of attributes. A relationship is an

association among several entities. The set of all entities of the same type is called an entity set

and the set of all relationships of the same type is called a relationship set. Overall logical

structure of a database can be expressed graphically by E-R diagram. The basic components of

this diagram are:

o Rectangles (represent entity sets)

o Ellipses (represent attributes)

o Diamonds (represent relationship sets among entity sets)

o Lines (link attributes to entity sets and entity sets to relationship sets)

Relational Model:

It is the current favorite model. The relational model is a lower level model that uses a

collection of tables to represent both data and relationships among those data. Each table has

multiple columns, and each column has a unique name. Each table corresponds to an entity set or

relationship set, and each row represents an instance of that entity set or relationship set.

Relationships link rows from two tables by embedding row identifiers (keys) from one table as

attribute values in the other table. Structured query language (SQL) is used to manipulate data

stored in tables.

The relational data model is the most widely used data model, and a vast majority of current

database systems are based on the relational model. The relational model is at a lower level of

abstraction than the E-R model. Database designs are often carried out in the E-R model, and

then translated to the relational model.

Other Data Models:

Object-based data models (Object-oriented and Object-relational):

Object oriented data model is extension to E-R model with the notion of encapsulation,

methods (functions) and object identity. It is based on collection of objects, like the E-R

model. An object contains values stored in instance variables within the object.

Network model:

In network model, data are represented by the set of records and relationships among data

are represented by links.

Hierarchical model:

Hierarchical model also represents data by a set of records but records are organized in

hierarchical or order structure and database is a collection of such disjoint trees. The nodes of

the tree represent record types. Hierarchical tree consists one root record type along with zero

more occurrences of its dependent subtree and each dependent subtree is again hierarchical.