How is Data Stored in a Hierarchical Database?

Introduction to Hierarchical Databases

A hierarchical database is one of the databases in which the data are arranged in a tree structure in which all the records are interconnected. The data is placed in a record-based manner, where a record is a group of fields, and each field must contain only one value. The hierarchical model requires that every child has only one parent and that every parent can have numerous children.

Structure of Hierarchical Databases

Root Record

A hierarchical database begins with just one record, the root record, in the record hierarchy.

Segments or Fields

Each record is divided into segments or fields representing specific attributes or data elements.

Parent-Child Relationships

They refer to data management where each record to be established maintains one ‘parent’ and can have one or more ‘children.’

Tree Structure

The data is structured as a tree, with the root at the top and subsequent levels forming branches, mirroring a natural hierarchy.

Record Identification

A unique key identifies every record, and relationships are maintained through pointers or links between parent and child records.

Traversal

Accessing data involves traversing the tree structure, starting from the root and navigating to specific records based on the desired path.

Advantages of Hierarchical Databases

- Simplicity: The one-to-many organization of data makes traversing the database simple and fast.

- Flexibility: The separation of tables from physical storage structures allows for easy addition or deletion of information without affecting the entire database.

- Compatibility: Most major programming languages offer functionality for reading tree structure databases.

Disadvantages of Hierarchical Databases

- Inflexibility: However, the one-to-many structure is not useful when the structure involves pinning and cannot elaborate relations in which each child node will have many parent nodes.

- Time-consuming Searching: The data structure employed is a tree, which means that whenever there is a need to search for something or a particular item, there is a need to search from top to bottom in a sequential manner, and this can easily take time.

- Data Redundancy: The hierarchical model can be highly redundant, where one has to store data in several different entities within the same model.

Examples of Hierarchical Databases

- Information Management System (IMS): Example of one of the most common hierarchical DBMSs for managing hierarchical data in applications such as banking and telecommunications.

- Windows Registry: It is used in the Windows Registry, which stores configuration information of the Microsoft Windows Operation System.

Hierarchical Databases vs. Relational Databases

Whereas hierarchical databases arrange the information in trees, relational models have data in related tables. The key differences are:

- Data Structure: The former is tree-shaped; the latter is tabular. 

- Relationships: While hierarchical databases can only accommodate one to many relationships, the relational database can even accommodate many relationships.

- Flexibility: In my opinion, relational databases are more flexible, or at least schema changes do not have severe consequences for existing applications.

Conclusion

The first form of database model initiated is the hierarchical database model to facilitate easy storage and retrieval of data within trees. Even though they cannot effectively manage complex relationships and need more space, hierarchical databases are popular in applications that demand high performance and availability, such as banking, healthcare, and telecommunication applications.