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 /