BT2102 Tutorial 3

Total Participation means...

• The entity is related to records in another entity, but not necessarily all

• The entity is linked with all other entities in our database

• The entity must participate in a relationship to exist

• The entity cannot participate in any relationships

What are the 2 main keys required in the Logical Data Model?

• Unique Keys and Foreign Keys

• Composite Keys and Unique Keys

• Primary Keys and Foreign Keys

• Primary Keys and Secondary Keys

What is the definition of a Primary Key?

• A key used for encryption purposes

• A key that uniquely identifies any data row of the table

• A key that is used for joining tables in a database

• A key that is used for sorting data in ascending order

When should a Composite Primary Key be used?

• When a single attribute of a table cannot uniquely identify a row

• When a table has no primary key

• When a table has a large number of records

• When a table has multiple foreign keys

What is the purpose of a Foreign Key?

• To define the structure of data elements

• To connect two tables and prevent invalid data insertion

• To uniquely identify each row in a table

• To encrypt sensitive data in a table

What is the definition of a Strong Entity?

• An entity that is used for data encryption

• An entity that depends on the existence of another entity

• An entity that has a uniquely identifiable Primary Key

• An entity that has no Primary Key

What is the definition of a Weak Entity?

• An entity that has a uniquely identifiable Primary Key

• An entity that cannot be uniquely identified by its attributes alone

• An entity that depends on the existence of another entity

• An entity that is linked to a strong entity

What does Cardinality tell us in a relationship?

• The total number of relationship occurrences for an entity participating in a relationship

• The maximum number of relationship occurrences for an entity participating in a relationship

• The minimum number of relationship occurrences for an entity participating in a relationship

• The average number of relationship occurrences for an entity participating in a relationship

What is the purpose of Normalisation in a database?

• To create a visual representation of the database schema

• To remove redundancy in database structure and reduce update anomalies

• To increase update anomalies in the database

• To introduce redundancy in database structure

What is the goal of 1st degree normalisation (1NF)?

• To combine schemas for strong entities

• To remove transitive functional dependencies

• To ensure the primary key is not dependent on other keys

• To remove repeating groups within the table