Databases

Question 1

What is an entity?

Answer 1

• Category of object, person, event or things of interest about which data needs to be recorded

Question 2

What are attributes?

Answer 2

• Characteristics or other information about entities

Question 3

What is a primary key?

Answer 3

• A unique identifier for every entity in a database table

Question 4

What is a foreign key?

Answer 4

• An attribute in a table which is the primary key in another related table
• This joins the two tables

Question 5

Why are databases normalised?

Answer 5

• So that they can be efficient without any compromise to the integrity of their data, ensuring entities contain no redundant or repeated data

Question 6

What is 1NF?

Answer 6

• Stands for First Normal Form
• No repeated data within entities
• Data is atomic, each field is unique

Question 7

What is 2NF?

Answer 7

• Stands for Second Normal Form
• Must be in 1NF
• Non-key attributes must depend on every part of the primary key

Question 8

What is 3NF?

Answer 8

• Stands for Third Normal Form
• Must be in 2NF
• “All non-key attributes depend on the key, the whole key and nothing but the key”