ICT701 Relational Database Systems Assignment

DBMS - Data Models

Data models characterize how the logical structure of a database is demonstrated. Data Models are principal entities to present reflection in a DBMS. Data models characterize how data is associated with one another and how they are processed and stored inside the system.

The absolute first data model could be flat data-models, where every one of the data utilized is to be kept in a similar plane. Prior data models were not all that logical, henceforth they were inclined to present heaps of duplication and update anomalies.

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Entity-Relationship Model

Entity-Relationship (ER) Model depends on the idea of true entities and relationships among them. While detailing genuine situations into the database model, the ER Model makes an entity set, relationship set, general properties and imperatives.

ER Model is best utilized for the applied structure of a database.

ER Model depends on −

•             Entities and their qualities.

•             Relationships among entities.

These ideas are clarified beneath.

•             Entity − An entity in an ER Model is a certifiable entity having properties called attributes. Each trait is characterized by its arrangement of qualities called domain. For instance, in a school database, an understudy is considered as an entity. The understudy has different attributes like name, age, class, and so forth.

•             Relationship − The logical association among entities is known as a relationship. Relationships are mapped with entities in different manners. Mapping cardinalities characterize the number of relationships between two entities.

Mapping cardinalities −

o             one to one

o             one to many

o             many to one

o             many to many

Relational Model

The most prevalent data model in DBMS is the Relational Model. It is more logical a model than others. This model depends on the first-request predicate rationale and characterizes a table as an n-ary connection.

The principal features of this model are −

•             Data is put away in tables called relations.

•             Relations can be normalized.

•             In standardized relations, values spared are atomic values.

•             Each row in a relation contains a unique value.

•             Each section in a relation contains values from a similar domain.