February 02, 2020
Amitraj
Hierarchical Model
This database model organises data into a tree-like-structure, with a single root, to which all the other data is linked. The heirarchy starts from the Root data, and expands like a tree, adding child nodes to the parent nodes.
->In this model, a child node will only have a single parent node.
->This model efficiently describes many real-world relationships like index of a book, recipes etc.
-> In hierarchical model, data is organised into tree-like structure with one one-to-many relationship between two different types of data, for example, one department can have many courses, many professors and of-course many students.
3. Many children per parent.
4. Distribute data in terms of relationships.
5. Improve data sharing.
Disadvantages of Hierarchical Model
4. One parent per child.
5. Complex (users require physical representation of database)
6. Navigation system is complex.
This database model organises data into a tree-like-structure, with a single root, to which all the other data is linked. The heirarchy starts from the Root data, and expands like a tree, adding child nodes to the parent nodes.
->In this model, a child node will only have a single parent node.
->This model efficiently describes many real-world relationships like index of a book, recipes etc.
-> In hierarchical model, data is organised into tree-like structure with one one-to-many relationship between two different types of data, for example, one department can have many courses, many professors and of-course many students.
Basic Concepts -
A hierarchical database consists of a collection of records which
are connected to one another through links.
-> A record is a collection of fields, each of which contains only one
data value.
-> A link is an association between precisely two records.
-> The hierarchical model different from the network model in that the records are organized as collections of trees rather than as
arbitrary graphs.
Advantages of Hierarchical Model
1. Easy to understand.
2. Performance is better than relational data model.
4. Distribute data in terms of relationships.
5. Improve data sharing.
Disadvantages of Hierarchical Model
1. Difficult to access values at lower level.
2. This model may not be flexible to accomodate the dynamic needs of an organisation.
3. Deletion of parent node result in deletion of child node forcefully
Extra space is required for the storage of pointers.
5. Complex (users require physical representation of database)
6. Navigation system is complex.
