The database model, commonly known as the data model, describes the way in which the database is structured in the database management system. The objective of a database model is to organize the data logically and physically. It also establishes and identifies the relationships between different records in the database. A database model comprises three components, which are given below-
(1) Structural part of the database model, consisting of a set of rules according to which databases can be constructed.
(2) Manipulative part of the database model, defining the types of operations that are allowed on the data (this includes the operations that are used for updating or retrieving data from the database and for changing the structure of the database).
(3) Possibly a set of integrity rules, which ensures that the data is accurate.
The various database models are given below:
Record-Based Data Models:
A record-based data models are used to specify the overall logical structures of the database. In the record-based models, the database consists of a number of fixed-format records possibly of different types. Each record type defines a fixed number of fields, each typically of a fixed length. Data integrity constraints cannot be explicitly specified using record-based data models. There are three principal types of record-based data models-
(1) Hierarchical Data Model- In this model, the data is arranged in a ‘hierarchical’ structure which describes the relationship of the records of the table in a ‘tree-like’ or ‘parent-child’ structure as shown below. In this model, the records are represented as nodes. They are linked with other superior records on which they are dependent and also on the records which are dependent on them. In the hierarchical database model, every record has a single owner/parent. The operations that can be performed on the hierarchical model are retrieval, insertion, deletion, and modification of records.
(2) Network Data Model- In this model, the data is represented by establishing a relationship between the records. This model is an improvement over the hierarchical database model. The records in this model can be linked with many records. In other words, in this model, a record can have multiple parent and child records.
(3) Relational Data Model- In this model, the data is organized in the form of rows and columns to form a table and the tables can be related to each other for sharing the data as shown below. The relational model is the most powerful database model since its design is easier as compared to other database models.
Object-Based Data Models:
Object-based data models are used to describe data and its relationships. It uses concepts such as entities, attributes, and relationships. It has flexible data structure capabilities. Data integrity constraints can be explicitly specified using object-based data models. The following are the common types of object-based data models-
(1) Entity-Relationship- It is a logical database model, which has a logical representation of data for an enterprise of business establishment.
(2) Object-Oriented- It is a logical data model that captures the semantics of objects supported in object-oriented programming. It is a persistent and sharable collection of defined objects. It has the ability to model a complete solution. Object-oriented database models represent an entity and a class.
Physical Data Models:
The physical data model represents the actual implementation of the Logical Data Model. A physical data model shows all the table structures including column names, column data types, column constraints, primary key, foreign key, and the relationship between tables.