A relational database consists of a collection of tables, each of which is assigned a unique name. It has a structure similar to a two-dimensional table.

A relation consists of:

A**Relational Schema** specifies the relation’s name, its attributes and the domain of each attribute. If **R** is the name of a relation and A_{1}, A_{2}, …, A_{n} is a list of attributes representing R then R(A_{1}, A_{2}, …, A_{n}) is called a relational schema. Each attribute in this relational schema takes a value from some specific domain called Domain(A_{i}).

Eg:- PERSON(PERSON_ID : integer, NAME : string, AGE : integer, ADDRESS : string)

The degree of this relation is 4.

Total number of attributes in a relation denotes the**degree of a relation**.

A**Relation Instance** denoted as **r** is a collection of tuples for a given relational schema at a specified point of time. A relation state r of the relation schema R(A_{1}, A_{2}, …, A_{n}), denoted by **r(R)**, is a set of n-tuples.

r = {t_{1}, t_{2}, …, t_{m}}

where each m-tuple is an ordered list of n values.

t = < v_{1}, v_{2}, …, v_{n} >

where each v_{i} belongs to domain(A_{i}) or contains null values.

In this instance m = 3 and n = 4.

In a relation, tuples are not inserted in any order. Ordering of tuples is not defined as a part of a relation definition. However, records may be organized later according to some attribute value in the storage system and such organization depends on the requirement of the underlying database application.

A relation consists of:

- Relational Schema
- Relation Instance

A

Eg:- PERSON(PERSON_ID : integer, NAME : string, AGE : integer, ADDRESS : string)

The degree of this relation is 4.

Total number of attributes in a relation denotes the

A

r = {t

where each m-tuple is an ordered list of n values.

t = < v

where each v

In this instance m = 3 and n = 4.

In a relation, tuples are not inserted in any order. Ordering of tuples is not defined as a part of a relation definition. However, records may be organized later according to some attribute value in the storage system and such organization depends on the requirement of the underlying database application.