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.
The hierarchical database model uses the hierarchic sequence that always starts at the left side of the tree. The most widely used database model is relational model.
Give an example of the hierarchical model?
IMS is a hierarchical database management system. Information management system IMS introduced by IBM in 1968.
Diagram of hierarchical database model
What are some limitations of the hierarchical database model?
Disadvantages of the hierarchical model
- Hierarchical model is Complex.
- One parent per child is allowed in hierarchical model.
- Data must be organized in a hierarchical fashion and it is done without compromising the information.
- There is a Lack of structural independence in hierarchical model.
- Navigation system is complex in in hierarchical model.
- In Hierarchical model, Data is independent.
- Hierarchical model does not support Many too many relationships.
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.
| Difference | Hierarchical Data Model | Network Data Model |
| Basic | There is a parent to child type Relationship between records. | Pointers or links are used to show a Relationship between records. |
| M:M
Relationship |
Hierarchical Database Model does not support M:M relationships . | Network Database Model supports M:M relationships . |
| Data Inconsistency | Possible during the data updation and deletion. | No Data inconsistency. |
| Traversing | Traversing of data is complex. | Node can be accessed from parent to child and similarly from child to parent. This makes the Data traversing very easy. |
| Structure | Hierarchical Database Model supports tree like structure . | Network Database Model supports the graph like structure . |
| 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
The hierarchical database model depicts a set of _____ relationships?
Topic Covered
Hierarchical Model with examples and characteristics.