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.
Get an assignment related to this topic on ICT701 Relational Database Systems.
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.
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