Relational Database Structure Flashcards
What is a relation?
A table with columns and rows
What is a tuple?
A row of a relation. They can appear in any order.
What is an attribute?
A named column of a relation. It can appear in any order.
Every attribute is defined by a domain, which may be distinct or not.
What is the degree?
The number of attributes in a relation.
What is the cardinality?
The number of tuples in a relation.
What is a relational database?
A collection of normalised relations with distinct relational names.
What is a superkey?
Attribute/s that uniquely identify a tuple within a relation.
What is a candidate key?
A superkey such that no proper subset is a superkey within the relation.
BASICALLY all possible primary keys.
What is a primary key?
The candidate key that is selected to identify tuples uniquely.
What is an alternate key?
Candidate keys not selected
What is a foreign key?
Attribute/s within one relation that matches the candidate keys of some relation
