Data is most important for business organizations as they store and process it in database management systems. A database management system helps users to view their data as they want by hiding the storage details.
Database models are used to abstract the data to the users. Hierarchical and relational database models are most commonly used in building databases.
Hierarchical Database vs Relational Database
The difference between hierarchical databases and relational databases is that hierarchical databases store data in the form of a tree with parent and child nodes, whereas relational databases store data in tables with rows and columns as entities and attributes. A hierarchical database contains duplicate data, but relational databases do not.
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A hierarchical database is the first generation database system used in applications to store and retrieve data. It is used in IBM mainframes even today.
It is a simple database structure but not suitable for storing complex and large data sets. Retrieval of data from this table is time-consuming.
On the other hand, relational databases models are the second-generation database systems that overcome the disadvantages of hierarchical databases by storing the data in tables, view, and connecting the databases with relationships.
It ensures that data is redundant in the tables that make it easy to retrieve, modify, and update.
Comparison Table
| Parameters Of Comparison | Hierarchical Database | Relational Database |
| Developed by | IBM in 1968 | E.F. Codd in 1970 |
| Generation | It is a First generation data model. | It is a Second generation data model. |
| Structure | A Tree structure that has parent nodes and child nodes | The Tabular form with rows and columns |
| Relationships | One-one,one-many | One-one,one-many,many-many |
| Data retrieval | The tree must be traversed from the root node to the required node | Using SQL query language. |
What is Hierarchical Database?
The hierarchical data model is the first data model used in traditional database systems developed by IBM in 1968. It is a model where the data is stored in a parent-child model where the child has only one parent.
It forms a tree-like structure where child nodes are the records that are connected via links. The first node in the tree is called the root node that does not have any parent node.
The parent node can have multiple child nodes but a child must be connected to only the parent node. Hence the database model satisfies one-one and one-many relationships.
The biggest advantage of a hierarchical database is that data access is easy and predictable. The retrieve and update are easily optimizable.
The biggest disadvantage of the database is that links cannot be modified as they are hardcoded. If there is any requirement for modification to the database, then the whole database must be redesigned.
The hierarchical databases are simple but flexible. It stores redundant data that increases complexity in retrieving the data.
As the hierarchical database has to be coded in the application, any change in the database requires the developer to change the code of the application.
Hierarchical databases are still used in the IBM mainframes but are not preferred for modern applications.
What is Relational Database?
The relational database model was developed in 1970 by E.F. Codd. It stores the records in the tables. The tables consist of rows and columns where the row denotes entities, and the column denotes attributes of the records.
Tables are linked with relations only when they share common attributes. Relational databases are user-friendly, programming friendly, and are preferred in industries over hierarchical databases.
Some of the relational database management systems are Oracle, DB2, MS-SQL Server, and Informix.
A relational database is not dependent on applications, and any changes in the database will not affect the application programming. This database is also suitable for defining complex relationships among tables easily.
In relational database systems, the logical structure is stored separately from the physical structure of the data. This helps to manage the structures differently without affecting each other.
Relational databases follow integrity rules to eliminate duplicate data into the tables. The SQL query language is used to retrieve the data from the database with consistency and accuracy.
Relational databases ensure ease of access of required databases by maintaining consistency. It is also easy to backup, import, and export the data easily at the time of emergency. Relational databases comply with an ACID property also.
Main Differences Between Hierarchical Database and Relational Database
- The hierarchical database has to be coded within the application to use, whereas relational databases are independent of the application.
- Hierarchical database stores data in the form of parent and child nodes forming a tree structure, whereas a relational database stores data in the rows and columns of a table.
- A hierarchical database implements only one-one and one-to-many relationships, whereas a relational database also implements many-to-many relationships.
- The whole tree has to be traversed to retrieve data in a hierarchical database, and SQL query language is used in relational databases to retrieve data.
- Hierarchical Database is the first generation database system, and relational database is the second generation database.
- https://www.google.co.in/books/edition/Introduction_to_Database_Systems/y7P9sa2MeGIC?hl=en&gbpv=0
- https://books.google.com/books?id=TFrbhHHxuXUC&printsec=frontcover&dq=beginning+mysql&hl=en&newbks=1&newbks_redir=1&sa=X&ved=2ahUKEwidpozo5O30AhWRTmwGHYJcChQQ6AF6BAgFEAI
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Sandeep Bhandari holds a Bachelor of Engineering in Computers from Thapar University (2006). He has 20 years of experience in the technology field. He has a keen interest in various technical fields, including database systems, computer networks, and programming. You can read more about him on his bio page.
