Saturday, 16 October 2021

Introduction to Relational model

The relational model uses a collection of tables to represent both data and the relationships among those data. Tables are logical models. It is a combination of three components such as structural, integrity and manipulative parts.

Structural part: The structural part defines the database as a collection of relations.
Integrity part: The database integrity is maintained in the relational model using primary key and foreign key.

Manipulative part: The relational algebra and relational calculus are the tools used to manipulate data in the database. This relational has a strong mathematical background.

Features of Relational model:

Relational data model is the primary data model, which is used widely around the world for data storage and processing. This model is simple, and it has all the properties and capabilities required to process data with storage efficiency.

Attribute: Each column in a Table is called as an attribute. Attributes are the properties which define a relation. e.g., Sid, Sname, DOB

Degree: The total number of attributes which are present in a relation is called the degree of the relation.

Tuple: A single row of a table, which contains a single record for that relation, is called a tuple.
Cardinality: Total number of rows present in the Table

Relation instance: A finite set of tuples in the relational database system represents relation instance. Relation instances do not have duplicate tuples.

Relation schema: A relation schema describes the relation name (table name), attributes, and their names.

Relation key:
Each row has one or more attributes, known as relation key, which can identify the row in the relation (table) uniquely.

Attribute domain: Every attribute has some pre-defined value scope, known as attribute domain.


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