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.
When we go through the structure of
One to many or one to one relationships
Allowed the network model to support many to many relationships
One to One,
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
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
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
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
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
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
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.