Database Model

Database model describes the structure of a database. Data model is collection of conceptual tools for describing data, relationship etc. There are different type of database model which are as follows:

• Hierarchical Database Model 

Hierarchical database model is a database which records are logically organized into a hierarchy of relationship. It organizes the data into a tree-like structure (pattern). The records of hierarchy are called nodes. In this model of database, each node is related to the others in a parent-child relationship. This database model’s parent record may have one or more child record and a child nodes will only have a single parent node. Its searching is fast and easy, if parent is know. It is organised into ‘One-to-Many’ relationship.

Advantages

1. It is the easiest model of database.
2. Searching is fast and easy, if parent is known.
3. It supports ‘One-to-Many’ relationship.

Disadvantages

1. It is traditional database model (old model).
2. It can not support ‘Many-to-Many’ relationship.
3. When the parent node is deleted, all the child nodes are deleted automatically.

• Network Database Model

It is a modified version of the hierarchical database (extension of the Hierarchical database model). In this database model, each nodes are allowed to have more than one parent. Searching is faster than hierarchical database model. And it is more flexible than hierarchical database model. Its structure is more complicated and less user-friendly than hierarchical database model/structure. Before relational database model was introduced this database is mostly use database model. It accept ‘many-to-many’ relationship. 

Advantages 

1. It is more flexible than hierarchical database model.
2. It accepts ‘many-to-many’ relationship. 
3. It has lower redundancy than hierarchical database model. 
4. Searching is faster. 

Disadvantages 

1. It is less user-friendly compared to hierarchical model.
2. it is open to all so it is less secured.
3. It is complex database model. 

• Relational Database Model

The database model which is arranged in two-dimensional tables is known as relational database model. It is very easy for a user to develop and understand. The basic structure of data in the relational model is tables. In this database model, tables are known as relations. All the information related to particular subject is stored in rows of the table. Normalization of the database is possible. It has very less data redundancy rate. It is more complex that other database models. No processing can be done without establishing the data relationships.

Table 1                                                                            Table 2

Roll no.	First name	Last name		Id_st	Subject	Teacher
1	Peter	Buffet		111	Math	Mark
2	Harry	Parker		222	Science	Dre
3	Sanjay	Dhakal		333	English	Denial

Relational Table

Roll no.	Id_st	Marks
1	111	80
2	222	65
3	333	95

   

                               Fig    Relational database model

Advantage 

1. It has very less data redundancy rate. 
2. Normalization of the database is possible.
3. Rapid processing of database is possible. 

Disadvantages 

1. It is more complex than other models
2. It is very hard to understand so it is non-user-friendly. 
3. Its is expensive while setting and maintaining the database system.