The Hierarchical Data Model

  • Same as network model. The only difference is that in the hierarchical model, records are organized as trees rather than arbitrary graphs.
  • The record type at the top of the tree is usually known as root.
  • In general, the root may have any number of dependents and each of these dependents may have any number of low level dependents and so on.
Consider the hierarchical view of the above sample database of suppliers, items and quantities. Database Management System
  • In this tree structure supplier record type is the root node.
  • Here the relationship is expressed in the form of a tree with all the edges pointing to the leaf.
  • The operations on a hierarchical database are performed through a data manipulation language for hierarchical data model.
  • The various operations include retrieval, insertions , deletions and modifications of records.