The data models describe the structure and organization of data in the database. It also defines the schema, the relation between the stored data, data consistency, and constraints that are applied to the stored data.
A data model defines the structure of a database at a physical, logical, and view level. We can classify the data model into four categories.
Table of Contents
We will discuss each kind of data model in brief and observe how each data mode structures the data in the database.
Data Models in DBMS
Relational Data Models
This is the most familiar kind of data model, which incorporates the use of tables to store data and to define the relationship between the data.
The relational model is also termed the record-based model, and this is because the relational data model stores data in the form of records. Each table in the relational data model has a record of a particular type that has a fixed format, i.e. each record in a table will have the same format.
A table in a relational model has rows and columns where each column of the table represents the attributes present in the dataset. Each row of the table represents the entity or object, or record, and each record in a table is unique.
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The entity-relationship model describes the overall logical structure of enterprise schema. The ER model represents real-world entities and also the interaction between them, thereby defining the relationship between the entities. Most database designing tools use the ER model to draw the concept of the enterprise schema.
The entity-relationship model incorporates three basic structures entity sets, relationship sets, and attributes.
Moreover, an entity set is a set that contains entities of the same type. For instance, an employee entity set will represent all the employees in the enterprise.
Similarly, the relationship set represents a set of relations of the same type. For example, the relationship set advisor would represent the relationship between instructors and students.
An entity is described by a set of attributes. An attribute describes the characteristic of the entity. For example, the student entity can be described as a set of attributes such as name, age, address, etc.
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Object-Based Data Model
Nowadays, object-oriented languages such as C++, Java, ruby, python, etc., are used for developing software. This is why the object-based data model came into trend. The object-based data model is an extension of the entity-relationship model.
Think of the entity-relationship model extended with the concept of encapsulation, functions, and identity of the objects. Well, another model, i.e. Object-relational model can be designed using features of both the relational data model and object-based data model.
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Semi-structured Data Model
A semi-structured data model specifies data in such a way that entities of the same type may be specified with a different set of attributes.
Further, the semistructured data model contradicts the models we have studied above, which describe entities of the same type possessing the same set of attributes. The semistructured data model employs Extensible Markup Language to develop semistructured data.
Concluding the data model in database management, we can say that the relational model is the most familiar model used for developing a database. Before the relational model, the network data model and hierarchical data model were in trend.