AS Level Databases

Identify three databases that are storing information about you.

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Name three of the most commonly used database management systems.

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Explain what the terms table, field and record mean.

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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