AS Level Databases

Identify three databases that are storing information about you.

Name three of the most commonly used database management systems.

Explain what the terms table, field and record mean.

What is an entity in a database?

• A person, place, event, or object

• A unique identifier for a table

• A set of attributes in one table

• A group of similar data

What is a primary key?

• An attribute that can have multiple values

• A unique identifier for a table

• A candidate key that is an alternative

• A set of attributes in one table

What is the purpose of normalisation?

• To reduce data redundancy

• To increase the size of the database

• To create more tables

• To ensure data is not shared

What does a foreign key do?

• Refers to a primary key in another table

• Is a unique identifier for a table

• Is an attribute that can have multiple values

• Is a candidate key that is an alternative

What is the first normal form (1NF)?

• Entities do not contain repeated groups of attributes

• Entities are in 2NF and any non-key attributes depend upon the primary key

• Entities are in 3NF and all non-key attributes are independent

• Entities contain no non-key dependencies

What is a candidate key?

• An attribute or smallest set of attributes in a table where no tuple has the same value

• A unique identifier for a table

• A set of attributes in one table that refer to the primary key in another table

• An attribute that can have multiple values

What is the relationship between Student and Class?

• One-to-one

• One-to-many

• Many-to-one

• Many-to-many