4.10 - Fundamentals of databases

Question 1

What is an entity in a database? (2 points)

Answer 1

Something used to represent an object in the real world that can be distinguished from other objects

Can be a physical object (such as a person or a place) or a concept (such as an activity or a task) for which we need to record data in the database

Question 2

What is an attribute in a database? (2 points)

Answer 2

Something used to represent a property, a quality or a characteristic that describes an entity

E.g. the name of an employee, or the date and time that a booking was submitted

Question 3

What are the 2 types of identifiers in a databse?

Answer 3

Entity identifier/key attribute - an attribute/set of attributes used to uniquely identify each instance of an entity

Composite entity identifier - a set of the minimum number of possible key attributes combined together

Question 4

What are the 3 types of database relationships?

Answer 4

One-to-one - whenoneinstance of an entity is associated withonly oneinstance of another entity
E.g. each school is run by one head teacher

One-to-many - whenoneinstance of an entity is associated withmore than one instance of another entity
E.g. each student books many appointments

Many-to-many - whenmore than one instance of an entity is associated withmore than one instance of another entity
E.g. many students are taught by many teachers

Question 5

Define ‘relational database’.

Answer 5

A database where separate tables are made for each entity, and
relationships between entities are represented by foreign keys

Question 6

What are the 3 types of keys used in a database?

Answer 6

Primary key - a unique identifier that identifies each record in a table

Composite primary key - a primary key made up from two or more other keys

Foreign key - a linking attribute that joins two tables in a relational database by being a primary key in one and a foreign key in the other