Database Revision

Question 1

A compound key is an example of a primary key.

Describe what is meant by a compound key in a relational database

Answer 1

A key comprising two or more attributes which are foreign/primary
keys from other tables

Question 2

What is an entity occurence

Answer 2

A specific example of an entity is called an instance or entity occurrence. For example:

John Smith, Mary McLeod and Omar Shaheed are all entity occurrences found in the Studententity

Question 2

What is an entity

Answer 2

An entity is a person, place, thing.

E.g. in a school, possible entities might be Student, Teacher, Class and Subject.

Question 3

What is an attribute

Answer 3

An entity is described by its attributes. Each attribute is a characteristic of the entity.

For example, attributes of the Student entity would include:
studentID 
firstname 
surname 
dateOfBirth.

Question 4

What is a primary key

Answer 4

A combination of attributes that uniquely identifies one, and only one, entity occurrence .

Question 5

What is a foreign key

Answer 5

An attribute in one table that uniquely identifies a row of another table.