Relational Model concept

The relational model can represent as a table with columns and rows. Each row is known as a tuple. Each table of the column has a name or attribute.

Domain: It contains a set of atomic values that an attribute can take.

Attribute: It contains the name of a column in a particular table. Each attribute Ai must have a domain, dom(Ai)

Relational instance: In the relational database system, the relational instance is represented by a finite set of tuples. Relation instances do not have duplicate tuples.

Relational schema: A relational schema contains the name of the relation and the name of all columns or attributes.

Relational key: In the relational key, each row has one or more attributes. It can identify the row in the relation uniquely.

Example: STUDENT Relation

NAME	ROLL_NO	PHONE_NO	ADDRESS	AGE
Ram	14795	7305758992	Noida	24
Shyam	12839	9026288936	Delhi	35
Laxman	33289	8583287182	Gurugram	20
Mahesh	27857	7086819134	Ghaziabad	27
Ganesh	17282	9028 9i3988	Delhi	40

• In the given table, NAME, ROLL_NO, PHONE_NO, ADDRESS, and AGE are the attributes.
• The instance of schema STUDENT has 5 tuples.
• t3 = <Laxman, 33289, 8583287182, Gurugram, 20>

Properties of Relations

• The name of the relation is distinct from all other relations.
• Each relation cell contains exactly one atomic (single) value
• Each attribute contains a distinct name
• The attribute domain has no significance
• tuple has no duplicate value
• The order of tuple can have a different sequence