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DBMS Relational Model concept

DBMS Relational Model concept with DBMS Overview, DBMS vs Files System, DBMS Architecture, Three schema Architecture, DBMS Language, DBMS Keys, DBMS Generalization, DBMS Specialization, Relational Model concept, SQL Introduction, Advantage of SQL, DBMS Normalization, Functional Dependency, DBMS Schedule, Concurrency Control etc.

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Relational Model concept

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 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

  • 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
  • Attribute domain has no significance
  • tuple has no duplicate value
  • Order of tuple can have a different sequence

Next TopicDBMS Relational Algebra




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