Hierarchical Model with examples and characteristics.
What is the Hierarchical Model?
When we want to design the database, there is a variety of database models. Relational and network models are famous models. You can read the tutorial about these topics here by clicking the model name. In this tutorial, we will explore the database hierarchical model.
According to the hierarchical model, all the records have a parent to child relationship.
Give an example of the hierarchical model?
IMS is a hierarchical database management system. Information management system IMS introduced by IBM in 1968.
Figure: a hierarchical model
What are the characteristics of the hierarchical model?
Does not supports many to many relationships:
Deletion problem:
If a parent is deleted, the child has also deleted automatically.
Data hierarchy:
Data can be represented as a hierarchical tree as can be seen in the figure.
Each child record can have only one parent record:
Hierarchy through pointer:
Pointers are used to link the records. Pointer determines that which record is parent record and which one is child record.
Minimize disk input and output:
Parent and child records are stored close to each other on the storage device. It helps to minimize the hard disk input and disk output.
Fast navigation:
Due to the short distance between parent to child, database access time and performance is improved. Navigation through the database is very fast in a hierarchical model.
Predefined relationships between records:
All relationships are predefined. Root nodes, parents, and the child are predefined in the database schema.
Difficult to re-organize:
It is difficult to re-organize the database due to hierarchy. It is difficult to re-organize because parent to child relationships can be disturbed.
| Test Your Understandings |
1. Hierarchical model supports many to many relationships ? YES / NO
2. Hierarchical model is more complex than Network model ? YES / NO
2. One child can have only parent entity ? YES / NO
Topic Covered
Hierarchical Model with examples and characteristics.