Database Models are the models which helps us to visualize manner of data can be stored , manipulated and organized.The Database models are basically divided in to Three models.The database models shows the flow for data and its components also called entities.The database can me modeled in a tree like for or inverse tree like form or as complex relational form.We will discuss all database models with example on this series of article.
The database models are :
This model can also be called One to many database model which generally can be called a tree model in which entities are arranged in tree like form the parent is on top and the children are followed by hierarchy and so one.The image can help you more clearly to understand Hierarchical model of database more clearly. The parent or Root contents level one Child and the level one includes Level two child and so on.To access Level two child we have to go through level one child.
Network Model of Database break some rules of Hierarchical model , In this model the database is modeled in tree like form but the child elements can have more then one parents and the parents can have more then one child.Still the database models is based on tree models with little flexibility so the child and parent relation can be more flexible on Database.
Relational model of database model is also known as many to many models , In this model any node can connect to any node .This model of database brought the concept of primary key and foreign key to Connect or create relation between Database.This model is widely used model noways.The relational Database model creates new database management possibility.
Altering any Physical (user applications) or external schema without affecting the logical schema of database or the changes on logical schema which doesn’t effect any physical or external schema is Data Independence.Data independence feature of database carries Database management system to next level because it is possible to change database without affecting the data and logical schema.
Data Independence are categorized into two groups as Logical data Independence and Physical Data independence.Logical data independence resembles the character that conceptual schema can be changed without affecting the existing schema , while Physical data independence resembles that physical storage structures can be changed without affecting conceptual schema.