Comparison between hierarchical model, network model and relational model

Data models, Data structures, Data manipulation, Data integrity comparison

 

When we move with the data models such as hierarchical model, network model, relational model we can identify number of difference in terms of data structures, Data manipulation and Data integrity.

 

Characteristic	Hierarchical model	Network model	Relational model
Data structure
When we go through the structure of the hierarchical model we can identify that it used a method for storing data in a database that looks like a family tree with one root and a number of branches or subdivisions. That's why we can say that record types are organized in the form of a rooted tree. But in network model we can identify multiple branches emanating from one or more nodes. So some times it is like a like several trees which share branches. In relational model is that of a relation. Relation is a two-dimensional table. So the table can be used to represent some entity information or some relationship between them
Data structure	One to many or one to one relationships	Allowed the network model to support many to many relationships	One to One, One to many, Many to many relationships
In hierarchical model only one-to-many or one-to-one relationships can be exist. But in network data model makes it possible to map many to many relationships In relational each record can have multiple parents and multiple child records. In effect, it supports many to many relationships
Data structure	Based on parent child relationship	A record can have many parents as well as many children.	Based on relational data structures
In hierarchical model relationship based in terms of parent child. So a child may only have one parent but a parent can have multiple children. But in network data model a record can have many parents as well as many children. Relational data model is based on relational data structures
Data manipulation	Does not provide an independent stand alone query interface	CODASYL (Conference on Data Systems Languages)		Relational databases are what brings many sources into a common query (such as SQL)
In relational database it use powerful operations such as SQL languages or query by example are used to manipulate data stored in the database But in hierarchical data model it does not provide an independent stand alone query interface while network model uses CODASYL
Data manipulation	retrieve algorithms are complex and asymmetric	Retrieve algorithms are complex and symmetric			Retrieve algorithms are simple and symmetric
In hierarchical data model and network model retrieve algorithms are complex and symmetric But in relational data model retrieve algorithms are simple and symmetric
Data integrity	Cannot insert the information of a child who does not have any parent.	Does not suffer form any insertion anomaly.			Does not suffer from any insert anomaly.
In hierarchical data model we cannot insert the information of a child who does not have any parent. But in network model does not suffer form any insertion anomaly. relational model does not suffer from any insert anomaly
Data integrity	Multiple occurrences of child records which lead to problems of inconsistency during the update operation	Free from update anomalies.			Free form update anomalies
In network model it is free from update anomalies because there is only a single occurrence for each record set.In relational model it also free form update anomalies because it removes the redundancy of data by proper designing through normalization process. But in hierarchical model there are multiple occurrences of child records. which lead to problems of inconsistency during the update operation
Data intergirty	Deletion of parent results in deletion of child records	Free from delete anomalies			Free from delete anomalies
In hierarchical model it is based on parent child relationship and deletion of parent results in deletion of child records .But in network model and in relational model it is free from deletion anomalies. Because information is stored in different tables.