DBMS Data Models

DBMS Data Models

Data models describe how a database 's logical structure is modeled. Data Models are important entities in a DBMS to implement abstraction. Data models explain how data are related to each other and how they are processed and stored within the system.

Flat data models may be the very first data model, where all the data used should be held on the same plane. Earlier data models were not so scientific, so they were likely to introduce lots of anomalies in duplication and updating.

Entity-Relationship Model

The model of Entity-Relationship (ER) is based on the notion of real-world entities and their relationships. The ER Model produces entity set, relationship set, general characteristics and constraints while formulating real-world scenarios into the database model.

For the conceptual design of a database, the ER model is best used.

The model of ER is based on –

These concepts are explained below.

Mapping cardinalities −

• Entitiesand their attributes.
• Relationshipsamong entities.
• Entity:An entity in an ER model is a real-world entity that has attributes called properties. Each attribute is defined by its set of property-called values. For instance, a student is treated as an entity in a school database. The student has different characteristics, such as name, age, class, etc.
• Relationship-Relationship is called the logical relationship between entities. In different ways, relationships with individuals are mapped. The number of associations between two entities is specified by Mapping Cardinalities.
  • one to one
  • one to many
  • many to one
  • many to many

Relational Model

In DBMS, the most common data model is the Relational Model. It is a model that is more empirical than some. This model is based on the logic of the first-order predicate and describes a table as a reference of n-ary.

This model's key highlights are −

• In tables called relations, data is stored.
• Relationships could be normalised.
• Values saved in normalised relations are atomic values.
• Each row contains a unique value in a relation.
• In a relation, each column contains values from the same domain.