Types of Database Models
Database Models in DBMS:
A database is an organized collection of information or data, records arranged. There are mainly five types of Database Models in DBMS:
Types of Database Models in DBMS:
1. Hierarchical DBMS (HDBMS)
2. Network DBMS (NDBMS)
3. Relational DBMS (RDBMS)
4. Object-Oriented Database (OODB)
5. Distributed DBMS (DDBMS)
Hierarchical model in DBMS:
Hierarchical data model developed by IBM in 1968 and it introduced in IMS (Information Management System). This model is like a structure of a tree with the records forming the nodes and fields forming the branches of the tree. In this model, records are linked in the form of an organisational chart
Advantages of Hierarchical model:
(i) It is a simple, straightforward and natural method of implementing record relationships.
(ii) Hierarchical model is useful when there is some hierarchical character in the database.
Network model in DBMS:
In network database structure, a record type can have multiple owners. In network model, data are represented by records using links among them. It is an improvement over the hierarchical model, here we can have many to many relationships (M:M) among records.
Disadvantages of Network model:
(i) All records are maintained using pointers and hence the whole database structure becomes very complex.
(ii) Insertion, deletion and updation of any record would require pointer adjustments.
Relational model in DBMS:
In a Relational Database Model, the data organized in the form of rows and columns similar to a table. The tables are referred to as relations in a relational data model. Rows of the table are referred to as tuples and the columns of a table are referred to as attributes. A relational database model is defined as a database that allows you to group its data items into one or more independent tables that can be related to one another by using fields common to each related table.
Object based data model in DBMS:
Object Oriented Database (OODB) are dependent on the object oriented programming paradigm. It enables us to create classes, organize objects, structure an inheritance hierarchy and call methods of represents class-subclass link. The dash ( – – – – ) represents attribute-domain link.
Distributed Database in DBMS:
In the centralized database system, data stored or resides in one single location. But in a distributed database system, database stored in several computers.
The computers in a distributed system communicate and exchange data among one another using leased lines, telephone lines or other means of communication. These computers do not share a memory or a clock. Each of the computers in a distributed system participates in the execution of transactions. These computers say sites or nodes.