Basic Structure of Database & Relational Models

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Basic Structure of Database

Basic Structure of Database

A domain is atomic if elements of the domain are considered to be indivisible units.

Set of permitted values called the domain of the attribute.

A super key is a set of one or more attributes that taken collectively, allow us to identify uniquely a tuple in the relation.

Super key for which no proper subset is a super key. Such minimal super keys are called candidate key.

We shall use the term primary key to denote a candidate key that is chosen by the database designer as the principal means of identifying tuples within a relation.

A database schema, along with primary key and foreign key dependencies can be depicted pictorially by schema diagrams.

A query language(SQL) is a language in which a user requests information from the database.

Relational algebra operations:

  • Select σ
  • Project P
  • Union È
  • Set difference –
  • Cartesian product x
  • Rename ρ
  • Set Interaction  Ç
  • Natural Join
  • Division /

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