Class 12 | MySQL

Relational Data Model

In the relational data model, the data is organized into a table.(i.e. row and columns). These tables are called relations. A row in a table represents a relationship between a set of values. Since a table is a collection of such relationships, it is generally referred to as using a mathematical term relation, from which the relation data model derives its name.


Terms used in Relational model

A table storing logically related data.

This a pool of values from which the actual value appearing in a given column are drawn.

A row of a relation.

A column of a relation.

Number of attributes ina relation.

Number of rows in a relation.

It is a virtual table that does not really exist in its own right but it is instead derived from one or more base tables.

Primary key:
This refers to a set of one or more attributes that can uniquely identify tuples within a relation.

Candidate key:
All attribute combinations inside a relation that can serve as the primary key.

Alternate key:
A candidate key that is not the primary key is called a candidate key.

Foreign key:
A non-key attribute whose values are derived from the primary key of some other table.